Skull

SKULL (cranium), i.e., the skeleton of the head of vertebrates, consists of two main parts: the axial skull and the visceral skeleton. The axial skull is a cartilaginous or bony box enclosing and protecting the brain, organ of hearing, and organ of smell, and forming on the sides depressions for the orbits, in which the organ of vision with eye muscles is movably attached. The visceral S. represents the skeleton of the anterior part of the intestine, performing functions of capturing and crushing food (jaws, hyoid apparatus) and respiration (gill apparatus, larynx). The visceral skeleton and its musculature find support on the axial S., with which it enters into close connection. Embryonically, the axial and visceral skeletons of the head develop independently of each other from different sources. The axial S. develops from mesenchyme, the source of which are sclerotomes of the head somites. This mesenchyme concentrates around the anterior end of the notochord, under the base and around the brain, as well as around the already mentioned sense organs (membranous phase of S. development). The formation of cartilaginous tissue begins in the base of the S., on the sides of the notochord ("parachordalia"), and at the base of the forebrain ("cranial trabeculae" or "trabeculae cranii"). Due to the significant bend in the region of the midbrain, the paired trabeculae underlying the forebrain form a significant angle (often close to right) with the parachordalia lying at the base of the hindbrain. As a result, the anterior end of the parachordalia forms a projection directed into the cranial cavity (dorsum sellae). The trabeculae and parachordalia fuse with each other, forming the floor of the cartilaginous S., but between the posterior ends of the trabeculae a membranous space (fenestra basicranialis ant.) is preserved for a long time, in place of which in the adult animal there remains a pit in which the hypophysis lies (sella turcica of the human S.). The lateral parts of the S. are formed by the growth of cartilage upward on the sides of the brain. Sometimes in the orbital area there are also independent centers of chondrification. In addition, in front, around the organ of smell, and on the sides, behind the orbits, around the organ of hearing, cartilaginous capsules develop, which sometimes show certain signs of independence. The roof of the cartilaginous S. is never complete even in lower vertebrates - part of it retains a membranous character (upper fontanelles). In higher vertebrates, cartilage usually develops here only in the occipital region in the form of a bridge connecting the auditory capsules over the medulla oblongata (tectum synoticum). In the vast majority of vertebrates (with the exception of cartilaginous fish), cartilage is partly displaced and partly supplemented by bones, forming together the bony S. In the most ancient fishes and in modern sturgeons there is a continuous external armor of the head from numerous skin bones, which represent the product of the growth of skin scales. Some of these bones grow more significantly, enter into closer connection with the underlying primary S. and form the covering bones of the roof of the S. Typical covering bones of the roof of the S. are as follows: nasal, frontal, pre- and postfrontal, lacrimal and postorbital, supratemporal and squamosal, parietal and postparietal, jugal (nasalia, frontalia, prae-et postfrontalia, lacrimalia, postorbitalia, supratemporalia, squamosa, parietalia, postparietalia, jugalia). In the oral cavity, under the bases of the teeth, also develop superficial ossifications lying in the mucous membrane - covering bones of the floor of the S.: paired vomer and unpaired parasphenoid (vomera, parasphaenoideum), as well as the covering bones of the visceral skeleton. On the other hand, in the walls of the cartilaginous S., bones develop, increasingly displacing cartilage in higher vertebrates. In the occipital region, thus develop: basi-, exo-, and supraoccipital bones (basioccipitale, exoccipitalia, supraoccipitale); in the auditory area: pro-, epi-, and opisthotic bones (prootica, epiotica, opisthotica); in the

Figure 1. Anlage of the axial and visceral skull of a shark embryo: 1- gill arch; 2- hyoid arch; 3- mandibular arch; 4-trabecula; 5- nasal cavity; 6-telencephalon; 7-metencephalon; 8-pleurosphenoid cartilage; 9-cerebellum; 10- trigeminal nerve; 11- facial nerve; 12-medulla oblongata; 13- parachordale; 14- cartilage in the labyrinth capsule; 15- glossopharyngeal nerve; 16- vagus nerve; 17- occipital region; 18- vertebral anlage; 19- spinal ganglion.

orbital area: basi-, pra-, latero-, and orbitosphenoid bones, and in the olfactory area: mes- and exethmoid bones. The visceral skeleton develops from ectodermal mesenchyme, the source of which is at least partially the ganglionic plate. This mesenchyme concentrates in the partitions between successive visceral pouches, as well as

Figure 2. Primary skull of a sturgeon: 1-rostrum; 2- nasal opening; 3-orbit; 4-hyomandibular; 5- gill arch with split upper end; 6-labyrinth capsule; 7- neural arch; 8- chorda; 9- ribs; 10- parabasale; 11- gill arch; 12- copulae; 13- hyoideum; 14- lower jaw; 15- palatoquadrum; 16- symplecticum.

in front of the first pouch in the oral region, forming a series of visceral arches surrounding the head section of the intestine (oral cavity and pharynx) on the sides. These arches chondrify and in doing so break down into several parts each. The anterior arch is called the mandibular arch, the second is the hyoid arch, and the following are the gill arches. The mandibular arch divides into two parts, forming in lower vertebrates the primary upper and lower jaws. The hyoid arch also divides mainly into two parts: the hyomandibular part attached to the auditory capsule of the S., which serves in most fishes as a suspensorium for the jaws, and the lower, proper hyoid (hyoideum). Gill arches as a rule divide into 4 parts each. In higher fishes all these parts ossify.

In the mandibular arch, usually only the posterior parts of the upper part ossify, where the quadrate bone, the posterior pterygoid of fishes, and the epipterygoid of terrestrial vertebrates develop, and the posterior part of the lower part, where the articular bone (articulare) develops. In addition, however, on the mandibular arch, as well as in front of it, a series of covering bones also develop in the mucous membrane. On the lower jaw- dental, splenial, angular, supraangular, dermoarticular (dentale, spleniale, angulare, supraangulare, goniale); on the upper- ecto- and entopterygoid and palatine bones (ecto- et entopterygoideum, palatinum). In front of the mandibular arch in the lips above- maxillary and premaxillary bones (maxilla et praemaxilla) (fig. 1,2,3).

In terrestrial vertebrates, the visceral skeleton undergoes very significant transformations: the upper part of the mandibular arch loses its significance as a S. and becomes part of the palate. The upper jaws are formed entirely from maxilla and praemaxilla. The upper part of the hyoid arch loses its significance as a suspensorium for the jaws and transforms into the auditory ossicle- columella (collumella) of the ear in amphibians, reptiles and birds, or the stapes (stapes) of mammals. In mammals, also the quadrate bone transforms into another auditory ossicle- _Fig. 3. roof of the sturgeon skull: 1- part of the lower jaw-^articulare^ 2-frontal + angular- forms the malleus of the ear (malleus). The angular part of the hyoid arch gives rise to the tympanic membrane of mammals. T. O. in the latter, from the composition of the jaws, a whole series of dermal bones lying in the area

cuium. joints of the lower jaw with the skull (through the intermediary of the quadrate bone), and forms part of the bones of the middle ear. From this it follows that in mammals there is a different articulation of the lower jaw with the skull than in lower vertebrates. The discovery of fossil reptiles occupying to a certain degree an intermediate position (theriodonts) has clarified many details of this process of transformation, as a result of which the lower jaw of mammals consists of only one bone, homologous to the dentary bone (dentale) of reptiles, which has acquired a new, independent articulation with the base of the skull through the progressive development and differentiation of its coronoid process. The lower part of the hyoid arch and one or two gill arches form in terrestrial vertebrates the hyoid bone with its horns. The arches behind are transformed into laryngeal cartilages. The bony skull of fish consists of a very large number of bones forming a more or less complete external armor of the head. The cranial box is relatively small, and the brain occupies only a small part of its cavity. The visceral skeleton forms the greater part of the skull, movably connected with the cranial box. The secondary jaws (maxilla and praemaxilla) are located in the upper lip and often (in bony fish) are movably attached only at their anterior ends to the olfactory region of the skull. The primary upper jaw is also attached to the skull only in front. Behind it is fixed on the auditory capsule mostly only through the intermediary of the upper part of the hyoid arch (hyomandibulare), which forms a suspension for the jaws ('suspensorium'). To the hyoid arch behind are attached the bones of the operculum. The gill arches surround the pharynx and are connected below and in front with the hyoid arch by means of a series of unpaired small bones. All these parts form a movable system participating both in the capture of food and in respiratory movements. In terrestrial vertebrates, as stated, there are very great transformations in the area of the visceral skeleton. The jaw arch articulates with the skull independently ('autostyly'), while the hyoid and gill arches are preserved only in the form of insignificant structures, little connected with the proper skull (hyoid apparatus and laryngeal cartilages). The proper cranial box in the most ancient terrestrial vertebrates (in stegocephalians) was surrounded by just as solid an armor of many dermal bones as in many ancient fish (dermal skull). This external armor supplements the dorsal wall of the brain box (since the primary skeleton here is underdeveloped), and from the latter it extends on the sides. In the space between the cranial box and the external armor is located the chewing musculature. In modern forms this armor is to a large extent reduced - the number of bones is smaller, it loses the character of a continuous covering due to the formation of temporal fossae. Thus, on the sides of the head instead of a continuous covering there is obtained a relatively light frame of bony bridges - temporal arches, strengthening the upper jaw on the axial skull (zygomatic type of skull). In mammals, as in some reptiles, there is only one such 'zygomatic' arch and sometimes in addition an orbito-temporal arch. The bones of the jaw arch, which in many reptiles and birds still form to a certain degree a movable system ('streptostyly'), are now firmly connected with the bones of the axial skull. Especially the epipterygoid completely enters into the composition of the wall of the skull, forming on the sides of the orbital area the bones known under the name of alisphenoids (of mammals), or the great wings of the sphenoid bone of the human skull. The upper jaw bones (maxilla and praemaxilla) are firmly fixed among other bones of the skull, and in monkeys and in man they fuse together with each other. For mammals in general it is rather characteristic the reduction in the number of skull bones by their fusion into some typical complexes. Thus, all 4 occipital bones (exoccipitalia, basi- and supraoccipitale) fuse together into one occipital bone, completely encompassing the foramen magnum and bearing a pair of occipital tubercles for articulation with the spine. With this bone very often fuse also the covering interparietal bones (tabularia and postparietalia of fish and stegocephalians), forming then the 'squama' of the occipital bone. The ossifications of the auditory capsule (prooticum and opisthoticum-mastoideum) fuse into one petrous bone (petrosum), to which in man are also attached the squamous (squamosum) and tympanic (tympanicum), forming the temporal (os temporale) bone of the human skull. In the orbito-temporal area the unpaired basi- and presphenoid fuse with the paired alisphenoid (epipterygoid of reptiles) and orbitosphenoid, forming one sphenoid (os sphenoideum) bone with 'great' and 'small' wings. In higher monkeys and in man with it also fuse the pterygoids. In the olfactory area several ossifications form the ethmoid bone (os ethmoideum) and several olfactory turbinates, attached to the ethmoid (ethmoturbinale), and sometimes also to the nasal (nasoturbinale) and sometimes to the maxillary bone (maxilloturbinale).

Figure 4. Roof of the skull of a stegocephalan: 1-septomaxillare (ha-riale); 2-praemaxillare; 3- maxillare; 4 - praefrontale; 5-lacrimale; 6-frontale; 7~ postorbitale; 8-postfrontale; 9-intertemporale; 10-parie-tale; 11- squamosum; 12- quadratum; 13 - tabulare; 14-postparietale; 15-supra-temporale; 16-jugale.

fusion into some typical complexes. Thus, all 4 occipital bones (exoccipitalia, basi- and supraoccipitale) fuse together into one occipital bone, completely encompassing the foramen magnum and bearing a pair of occipital tubercles for articulation with the spine. With this bone very often fuse also the covering interparietal bones (tabularia and postparietalia of fish and stegocephalians), forming then the 'squama' of the occipital bone. The ossifications of the auditory capsule (prooticum and opisthoticum-mastoideum) fuse into one petrous bone (petrosum), to which in man are also attached the squamous (squamosum) and tympanic (tympanicum), forming the temporal (os temporale) bone of the human skull. In the orbito-temporal area the unpaired basi- and presphenoid fuse with the paired alisphenoid (epipterygoid of reptiles) and orbitosphenoid, forming one sphenoid (os sphenoideum) bone with 'great' and 'small' wings. In higher monkeys and in man with it also fuse the pterygoids. In the olfactory area several ossifications form the ethmoid bone (os ethmoideum) and several olfactory turbinates, attached to the ethmoid (ethmoturbinale), and sometimes also to the nasal (nasoturbinale) and sometimes to the maxillary bone (maxilloturbinale).

The floor of the skull, in fish and lower terrestrial vertebrates lined with a long unpaired parasphenoid and paired vomers, forms together with the bones of the upper part of the jaw arch a support for the roof of the oral cavity, so-called primary hard palate, bounded on the outside by the maxillary and premaxillary bones. Both pairs of nostrils are located in fish outside the oral cavity, usually on the dorsal part of the olfactory area of the head. Only in dipnoans they lie under the upper lip. In amphibians and lower reptiles the pair of 'internal' nostrils or primary choanae open at the anterior edge of the palate between the maxillary bones and the vomer. In some reptiles from the maxillary bones develop horizontal outgrowths, shutting off some space under the olfactory area of the skull, where the choanae open. These outgrowths form the rudiment of a secondary hard palate, which separates the upper respiratory part of the oral cavity (ductus nasopharyngeus). The vomers fuse together and form a septum dividing this cavity. Behind the secondary palate it opens by means of 'secondary choanae'. Part of the primary choanae, connected with the Jacobson's organ, is preserved in the form of 'foramina incisiva'. With further development of the secondary hard palate into its composition also enter the palatal processes of the palatine bones, and sometimes also the pterygoid bones (crocodiles, whales), usually bounding the secondary choanae on the sides * The skull of mammals has a rather characteristic general appearance. The jaws are relatively high, the base of the skull is wide and the orbits are Figure 5. Skull of a lizard from below: 1- choanae; 2 -lateral window (roof of the palate); 3- interpterygoid fissure; 4-pterygoid; 5 - proc. paroticus; 6-basipterygoid joint; 7-quadratum; 8-proc. cultriformis;.9-transversum; 10-palatinum; 11-vo-mer.

Figure 6. Skull of a primitive reptile (tuatara) with two zygomatic arches, from the side: 2- frontale; 2-postfrontale; 3-parietale; 4-squamosum; 5-pterygoid; 6-quadrat. jugale; 7 - jugale; 8-epipterygoid; 9-sept, interorbitale (unossified); 10 - maxill.

widened (no interorbital septum). It is also characteristic the rather considerable growth of the cranial cavity, thanks to which the skull behind the orbits acquires a rounded shape, as well as the growth of the olfactory area. For monkeys, and especially for man, on the contrary, is characteristic the reduction in size of the olfactory part, but all the more considerable development of the cranial box, which advances from above onto the orbits and onto the olfactory area, so that the ethmoid plate becomes more and more inclined, finally taking in man a horizontal position. The jaws are reduced, and the axis passing through the facial parts becomes in man perpendicular to the axis passing along the base of the skull (fig. 4-9).

I. Shmal'gauzen.

The skull in an anthropological respect. For man in comparison with all other animals is characteristic the considerable development of the cerebral part of the skull (neurocranium) and the reduction of its facial part (splanchnocranium). According to the data of Hoor in a median-sagittal section the area of the face in man constitutes 25-45% of the cerebral, whereas in the most man-like monkey-chimpanzee - this ratio reaches 100-130 %. The capacity of the cranial cavity (cavum cranii) of adult humans varies approximately from 1,000 to 2,000 cm³, in most cases it approaches 1350-1550 cm*. The capacit

" " bone of the skull in anthropomorphic forms is much lower: for male gorillas on average about 500 cm³, for orangutans and chimpanzees even less. The large size of the brain is associated with a number of important morphological features of the human skull: strong development in height and rounding of the vault; very large parietal bones; protruding frontal section, extending downward over the face; oblique, rather than vertical as in other mammals, position of the occipital bone scale; pronounced downward bend of the base. The reduction of the visceral (facial) part of the skull is explained primarily by the far-reaching reduction of the chewing apparatus. Reduction

Figure 7. Skull of a mammal (dog) from below: 1 - praemaxillare; 2-for. inci-sivum; 3-maxillare; 4- pa-latinum; 5-choanae; 6-for. sup.; 8 - jugale; 9 - for. turidum; 10 -for. ovale; 11 - squamosum; 12 - auditory opening; 13-for. lacerum post.; 14^ tor. condyloid. (hypoglossus); 15 - condyl. occipit.; 16-for. occipitale; 17-bulla tympani; 18-basi-occipit.; 19-for. lacerum ant.; 20-sphenoid; 21 - pterygoid.

this is manifested in the relatively small size of the teeth, not separated by gaps (diastemas), in the shortening and widening of the palatal arch, in the less spread apart than in anthropomorphic forms, position of the zygomatic bones, in the slight forward projection of the upper jaw, in the weak development of the external bone relief, in particular in the absence of the sagittal crest, so typical for male gorillas, orangutans and partially chimpanzees. Many characteristic human features in the structure of the skull, especially its base, are connected with upright posture and the vertical direction of the longitudinal axis

Figure 8. Diagrams of the relationships of the jaw joint and auditory ossicles in reptiles: 1-dentale; 2-coronoid.; 3-quadratum; 4-proc. dorsalis; 5-proc. paroticus; 6-stapes; 7-extracolumella; 8- hyoideum; 9 - goniale; 10-arti- culare; 11-angulare; 12-suprangulare.

Figure 9. Diagram of the relationships of the jaw joint and auditory ossicles in mammals: 1-dentale; 2-cart. Meckeli; 3-proc. articularis; 4-malleus (articulare); 5- incus (quadratum); 6-stapes; 7-hyoideum; 8-tympanicum (angulare); 9- proc. folianus (goniale).

of the body. These include: the central location of the foramen magnum (foramen occipitale magnum), which is pushed forward and inclined from front to back, rather than backward as in all other mammals; the intensive development of the mastoid and styloid processes; the weakening of the muscular relief of the occiput, expressed in the disappearance of the transverse occipital crest. Among other specific features of the human skull should be noted: the relatively small thickness of the bones and the associated, more complete than in other higher primates, correspondence between the external shape of the skull and the brain capsule; the relatively weak expression of the supraorbital ridges; the protruding bone of the nose from the plane of the face; the so-called "anthropoid" form of the lower edge of the foramen rotundum, expressed in the sharp boundary between the entrance to the nasal cavity and the maxilla; the presence of a developed chin prominence. Along with differences, the human skull shows many common features with the skulls of other primates, especially with the skulls of narrow-nosed Old World monkeys (ossifying external auditory canal, lack of contact between the zygomatic and parietal bones in the lateral wall of the skull, absence of the third premolar tooth, etc.). From a phylogenetic point of view, the analogies with African anthropoid primates are particularly interesting, traceable through a number of secondary, evolutionarily indifferent features of the skull. Thus, unlike Asian anthropoids—the gibbon and orangutan—for humans, gorillas, and chimpanzees, the presence of frontal sinuses and a wide interorbital space is characteristic (Weinert). Specifically with the chimpanzee, man is close in the shape and size of the frontal sinuses, in the ratio of internal and external length of the skull, in the early disappearance in the process of ontogenesis of the intermaxillary bone, and in the very frequent (90-100%) presence of the "foramen spinosum" (foramen spinosum) at the base of the skull. Comparison of data from comparative anatomy, embryology, and paleoanthropology allows us to outline the main paths of phylogeny of the human skull. In the process of anthropogenesis, there undoubtedly took place: an increase in the total capacity of the skull, an increase in its height, an expansion and forward displacement of the visceral part of the frontal region, development of the chin prominence, formation of a protruding forward bony nose, general gracilization of the entire appearance of the skull, in particular a decrease in the thickness of the bones, weakening of prognathism (protrusion of the jaws), reduction of the supraorbital region and occipital relief. It is very probable that in the course of evolution, the transverse dimensions of the brain capsule increased somewhat more rapidly than the longitudinal ones; the result of this was the gradual brachycephalization of humanity (see Brachycephaly). The skulls of extinct species and genera of the family Hominidae—Pithecanthropus, Sinanthropus, Neanderthal man—occupy an intermediate position between anthropoid monkeys and modern humans in many features (capacity, height of the vault, chin, relief, etc.). The structure characteristic of the adult human skull is gradually formed ontogenetically. The primary membranous (primordial) skull of man is indistinguishable from that of an ape. By the time of birth, the capacity of the brain capsule reaches 350-400 cm³ (about 25% of the capacity of an adult). For the newborn and infant skull are also characteristic: very small dimensions of the facial part compared to the cerebral part (about 18%), thin bones, almost complete absence of muscular relief, in particular of the supraorbital region, presence of unossified connective tissue areas (fontanelles), relatively weak development of the base, pentagonal shape when viewed from above, slight protrusion of the bony nose and chin, presence of the frontal suture, etc. The further growth of the parts of the skull is uneven—the visceral part increases both absolutely and relatively much faster than the cerebral part. The most intensive growth of the skull occurs during the first year of life, when its length increases by 12 mm and its width by 14 mm. By the 12th year, the annual increase in both dimensions falls to 1 mm. From 28-30 years, the obliteration of the sutures between the individual bones of the skull begins. In old age, there is a reduction of the alveolar parts of the jaws, associated with the loss of teeth. Various disorders of the normal course of ontogenesis lead to the appearance of anomalous and pathological forms of the skull. These include, for example, microcephaly, macrocephaly, oxycephaly (see). A number of anomalies are caused by premature obliteration of the sutures and the resulting compensatory growth of the cranial cavity in one direction. Early obliteration of the coronal suture leads to a tower-shaped skull, of the sagittal suture—to an extremely elongated "boat-shaped" (scaphocephaly). Unilateral cessation of growth leads to the formation of a sharply asymmetrical "oblique" skull (plagiocephaly). Artificial deformations of the skull depend mainly on the action of various mechanical factors on the plastic head of a child, determined by the design of the cradle, methods of swaddling and carrying small children, etc. Sexual differences in the skull are expressed in man less sharply than in other higher primates. The female skull is smaller than the male in absolute dimensions, but larger in relation to height and body weight. Compared to the male, the female also has thinner bones, weaker muscular relief on them, a straighter forehead, slightly less protruding nose and chin, and rounder orbits. These differences are by no means absolute and are clearly revealed only in cumulative comparisons of cranial series belonging to different sexes. The study of racial variations of the skull has great anthropological importance. In the works of the 19th and early 20th centuries, greatest attention was paid to the comparison of various cranial indices, characterizing cranial series belonging to separate modern or ancient ethnic groups of humanity. The most widespread of these indices was the so-called "cephalic" (on the living) or "cranial" (on the skull) index, proposed by the Swedish anatomist Anders Retzius and giving the ratio of the greatest (parietal) width of the skull to its greatest length. Excessive preoccupation with indices led to craniometry (see) becoming detached from other methods of research and gave it a formalistic imprint. At present, leading anthropologists of the USSR, Western Europe, and America, in racial analysis, take into account not only indices but also absolute values of cranial diameters and angles, as well as qualitative "descriptive" features not subject to measurement (for example, degree of development of the supraorbital region, depth of the canine fossa, general contour in norma verticalis, etc.). Differences between the skulls of the main human races go mainly along the line of secondary features, which have no great evolutionary significance and do not provide a basis for conclusions about the morphological primitiveness of one or another of the currently living varieties of humanity. If these differences do involve essential evolutionary features, then the distribution between the races of "primitive" and "progressive" forms turns out to be so variegated that on the basis of the totality of features of the skull, none of them can be placed "above" or "below" another. For example, in the degree of protrusion of the jaws, Negroids (the "black" race) are "more primitive" than Europoids (the "white" race); in the slope of the forehead and development of the supraorbital region, there is a diametrically opposite relationship. The constructions of Günther, Lenz, Darre, and others, popular in fascist Germany, concerning the connection of racial features of the skull (primarily the cephalic index) with certain psychological qualities, are also devoid of any scientific basis. Cheboksarov. In man, two groups of cranial bones are distinguished: bones of the cranial vault (ossa cranii) and bones of the face (ossa faciei). The former include: the occipital bone (os occipitale), the sphenoid bone (os sphenoidale), the temporal bones (ossa temporalia), the parietal bones (ossa parietalia), the frontal bone (os frontale), and the ethmoid bone (os ethmoidale). The facial bones include: the nasal bones (ossa nasalia), the lacrimal bones (ossa lacrimalia), the vomer, the inferior nasal conchae (conchae nasales inferiores), the maxillary bones (maxillae), the palatine bones (ossa palatina), the zygomatic bones (ossa zygomatica), the mandible (mandibula), and the hyoid bone (os hyoideum). The connections of these bones are extremely diverse; all of them, with the exception of the mandible and hyoid bone, are immovable. The shape of the head skeleton is determined by the ratio of the vertical, transverse, and longitudinal diameters and the deviation between the cerebral and facial skull. The head rests with its entire weight on the spine, with which it articulates in the atlanto-occipital joint. On the skull, the vault and the base are distinguished. The first, corresponding to the convex external surface (fornix cranii externus), has a concave internal surface (fornix cranii internus). The base of the skull, consisting of massive, irregularly shaped bones, also has an internal surface (basis cranii interna) and an external one (basis cranii externa). The boundary between the vault and the base of the skull runs from the external occipital protuberance in both directions to asterion, from there to the squamosomastoid suture and the crest of the zygomatic process of the temporal bone.

Passes past the tuberculum articulare and along the crista infraorbitalis to the sutura spheno-zygomatica; then it goes along the edge of the wing of the sphenoid bone, which limits the fissura orbitalis superiorly and laterally, approaches the body of the sphenoid bone, from where, going in front of the base of the pterygoid process, it reaches the rostrum sphenoidale on both sides. Ontogenesis. In the first week of development, there is only the embryonic vesicle. On the 20th week, the laying of the nervous system, blood vessels begins, the amniotic fold, the primary segment appear. The head section is separated. At the end of the 1st month, there are rudiments of the eye and ear in the form of a small protrusion of the head section. Very sharp proportions: the head is almost half the length of the body due to the powerful development of the brain. The neck is absent. In the 2nd month, the rate of development slows down, bends of the brain are noticed; the hemispheres bend backward. The face begins to be defined in the second half of the 2nd month in a 15 mm embryo; in an 18 mm embryo, the nose is clearly visible. In the 2nd month, the auricle begins to straighten. The head begins to straighten, the cerebral skull is still large. The protrusions of individual parts of the Skull cease to be visible on external examination. By the end of the 3rd month, the detailing of the head forms is not yet complete. The cerebellum still forms a protrusion. The cerebral hemispheres move backward. The brain of a newborn externally resembles the brain of an adult. In the future, the details of the internal structure are developed. The Skull develops from mesenchyme. The bones of the head skeleton arise: 1) from the cartilaginous primordial Skull, 2) from the cartilaginous framework of the gill arch, 3) from the cutaneous-mucous area. The vault of the Skull consists of 3 areas. 1. Regio fronto-parieto-occipitalis; boundaries: in front - the upper edge of the orbit, behind - the superior nuchal line, on the sides - the superior semicircular line of the parietal bones. 2. Regio temporalis - the lateral parts between the superior semicircular line of the parietal bone and the zygomatic arch with an extension to the incisura mastoidea. 3. For practical purposes, Kupriyanov also includes the regio mastoidea in the vault. The skeleton of the regio fronto-parieto-occipitalis includes the squama of the frontal bone, the medial parts of both parietal bones, and the squama of the occipital bone. The squamous part constitutes the main part of the frontal bone. With its parietal edge, it adjoins both parietal bones via the coronal suture and with its sphenoidal edge (sutura spheno-frontalis) to the greater wing of the sphenoid bone. The outer surface is convex, on each side it has a tubercle (tuber frontale). Above the orbital edges are the superciliary arches (arcus superciliares), between them is the glabella (glabella). On the upper orbital edge, on its inner half, there are two notches: medially the incisura frontalis, laterally the incisura supraorbitalis; instead of the latter, there is sometimes an opening (foramen supraorbitale). The inner surface is smooth, mostly has impressiones digitatae and juga cerebralia, as well as Pachionian pits. Parietal bones - see Parietal bone. The squamous part constitutes the larger part of the occipital bone, it is flat, concave on the inside, convex on the outside and has a triangular shape; via the occipito-mastoid suture (sutura occipito-mastoidea) it is separated from the mastoid part of the temporal bone, via the lambdoid suture - from both parietal bones. On the inner (cerebral) surface of the squamous bone there is a cruciform elevation (eminentia cruciata), the upper and lateral limbs of which are formed by grooves, while the lower one is formed by a ridge going to the posterior circumference of the foramen magnum. In these grooves lie the venous sinuses of the dura mater. In the middle of the cruciform elevation is the internal occipital protuberance (protuberantia occipitalis interna). The outer surface of the squama of the occipital bone is divided by the superior nuchal lines, extending from the external occipital protuberance, into two parts: the upper relatively smooth triangular part (planum occipitale) and the lower rough one (planum nuchale). But in the superior nuchal lines, directed to the mastoid margin, there are often arcuate superior nuchal lines. From the external occipital protuberance, the crista occipitalis goes to the posterior circumference of the foramen magnum, from its middle go parallel to the superior nuchal lines, the inferior nuchal lines. The bones of the vault of the Skull consist of two plates - lamina externa and lamina interna, between which is the diploe, spongy substance, and on different areas the diploe is expressed differently, which explains the unequal thickness of the bone wall. The outer plate is thicker and stronger than the inner one, which explains why the inner plate is also called lamina vitrea. Regio temporalis. On the skeleton of this area, the planum temporale is expressed, composed of the squama of the temporal bone, the greater wings of the sphenoid, part of the parietal bone, the frontal process of the zygomatic bone, and the zygomatic process of the frontal bone; with a ridge (crista infratemporalis) this area is separated from the planum infratemporale. This area is inclined relative to the base of the Skull, and therefore between it and the zygomatic arch there is a space called the temporal fossa (fossa temporalis). Below the ridge there is also a depression - the infratemporal fossa, which is as it were a continuation of the temporal fossa; it communicates with the spheno-maxillary fossa, pterygo-palatine fossa, the orbit, which explains the spread of abscesses. The bone consists of three layers: outer and inner plates and spongy substance between them, but the latter is expressed insignificantly, therefore the bone is thinned and of all parts of the Skull it is the least stable. Regio mastoidea corresponds to the zygomatic process. The surface is rough, in its middle there is a fairly smooth area (trigonum Chipault), bounded above by the continuation of the root of the zygomatic arch, behind by the _g mastoid crest, in front by the upper-posterior edge of the circumference of the external acoustic porus. The practical significance of the triangle is that within its limits operative interventions are performed. The external base of the Skull has two parts - anterior and posterior. Within the anterior part are: the body of the sphenoid bone, the basilar process of the occipital bone, the inferior surfaces of the greater wings of the sphenoid bone, and part of the temporal bone. This part has a series of openings through which vessels and nerves pass. In front of the lateral crest (its beginning is the outer plate of the pterygoid process, which then goes to the styloid process and the mastoid process) lies the foramen ovale, medially 0.5 cm away is the internal carotid foramen and the anterior lacerated foramen. In front and outside the base of the angular spine is the foramen spinosum, inside the musculo-tubarial canal, on the medial side of the crest lie the external carotid foramen and the jugular foramen; finally, the stylo-mastoid foramen lies behind the styloid process. The area enclosed between the lateral crests is called the hilus, and its middle part is the guttural fossa, as it forms the vault of the nasopharynx. Medial to the infratemporal fossa lies the pterygo-palatine fossa; there is no lateral wall, but there is a slit communicating both adjacent fossae. The pterygo-palatine fossa passes into a canal (canalis pterygo-palatinus), which opens on the inferior surface of the hard palate; with the help of the sphenopalatine foramen it communicates with the nasal cavity. With the help of the foramen rotundum, the pterygoid fossa communicates with the middle cranial fossa, through the inferior orbital fissure - with the orbit. The internal base of the Skull consists of three processes - anterior, middle, and posterior. The anterior part is bounded by the edge of the lesser wings of the sphenoid bone and the anterior clinoid process. The middle cranial fossa is bounded in front by the edge of the lesser wings of the sphenoid bone and the limbus sphenoidalis, behind by the superior edge of the pyramid of the temporal bone and the wall of the sella turcica. In the middle part are located the optic foramen (a. ophthalmica and n. opticus), superior orbital fissure [nn. oculomotorius, trochlearis, abducens, ophthalmicus (I n. trigemini)], foramen rotundum [n. maxillaris (II n. trigemini)], foramen ovale [n. mandibularis (III n. trigemini)], foramen spinosum (a. meningea media), anterior lacerated foramen (n. petrosus superficialis). The posterior cranial fossa is bounded in front by the superior ridge of the pyramids and the dorsum sellae, and behind by the horizontal limb of the internal cruciform eminence of the occipital bone; in the center is located the foramen magnum, through which the medulla oblongata with arteries passes. On the posterior surface of the pyramid is located the internal auditory meatus (nn. facialis, acusticus); in addition, there are the following openings: posterior lacerated foramen (IX, X, XI pairs of cranial nerves, v. jugularis, a. meningea posterior), anterior condyloid foramen (n. et v. hypoglossi), mastoid foramen. The soft tissues in the areas are arranged as follows. In the regio fronto-parieto-occipitalis, the skin is of considerable thickness, over a large area it is covered with hair, contains a large number of sebaceous glands; the subcutaneous fat tissue is penetrated by a series of fibrous septa, which very firmly connect the skin with the underlying tendon-muscle layer.

Next comes the galea aponeurotica—a tendonous stretching common to both the m. frontalis and m. occipitalis. In front it begins from the supraorbital arches, the processus frontalis maxillae, at the root of the nose; behind it is on the squama of the occipital bone, above the lin. nuchiae super. The upper surface of the aponeurosis connects with the previous layer by connective tissue bridges, the lower surface

Figure 10. Vessels and nerves of the head from the side: 1-p. occipitalis major; 2-a. occipitalis; 3-n. occipitalis minor; 4-ram. auricularis post. n. facialis; 5-m. sternocleidomastoideus; 6-n. facialis; 7-a. et v. temporalis superficialis; 8-n. auriculotemporalis; 9-ram. frontalis a. temporalis superf.; 10-n. lacrimalis; 11 - n. supraorbit.; 12-a. supraorbit.; 13- ram. parietalis a. temporalis superf.

adheres to the loose cellular tissue, on the sides it passes into the temporal region and disappears in the cellular tissue of the cheek. The subaponeurotic cellular tissue is especially expressed in the vault. Finally comes the periosteum, connected with the bone loosely, except in the regions of the sutures. In the regio temporalis the soft tissues have the following layers: thin skin, less durable, connected with a layer of fat, under which is located the fascia superficialis, essentially a thinned continuation of the galea aponeuroticae, then comes the fascia temporalis—a strong temporal aponeurosis. The subperiosteal layer is very poorly expressed and the periosteum directly adjoins the bone. On the head there is a fairly developed vascular network; the main arterial trunks: a. supraorbitalis, a. frontalis, a. temporalis superficialis, a. auricularis posterior, a. occipitalis; these vessels are in the regio fronto-parieto-occipitalis, a. temporalis superficialis—in the regio temporalis (fig. 10-12). The venous system is arranged in three tiers: veins of the skin, veins of the diploe, sinuses. Nervous system. The nerves accompany the arteries (n. frontalis, n. auriculotemporalis, n. supraorbitalis, nn. temporales profundae ant. et post.). Lymphatic vessels collect into several groups of lymphatic glands: 1) in the region of gl. parotis—they collect lymph from the anterior part of the region; 2) behind and under the angle of the auricle is another group of glands and finally 3) the third group of glands is located at the place of attachment of m. trapezius (fig. 13). In the cavity of the Skull is contained the brain with its membranes and vessels, with the anterior cranial fossa of the internal base of the Skull containing the frontal lobes of the brain, in the middle—temporal lobes, in the posterior—cerebellum, medulla oblongata, beginnings of nerves and vessels. The type of Skull is determined by the ratio of the transverse and longitudinal diameters. The transverse dimension is taken at the level of tubera parietalia, and the longitudinal—between protuberantia occipitalis externa and glabella. To calculate the cranial index, the length is taken as 100, and the width is expressed in percentages, and thus the calculation is performed by the formula width × 100 / length. There are long-headed Skulls (dolichocephals), the index of which is 74.9 and less; medium-headed (mesocephals) with an index from 75.0 to 79.9; round-headed (brachycephals) with an index of 80.0 and higher. The height index is calculated by the formula height × 100 / length; the height of the Skull—the vertical dimension from basion (the anterior midpoint of the foramen magnum) to the vertex. With an index above 75.0—high Skull (hypsicephal); 70.0-75.0—orthocephal; below 70.0—platycephal. In addition, when determining the type of Skull, one should consider where its main mass is directed: toward the frontal or occipital region, with the linea biauricularis serving as a guide—a vertical line connecting the external auditory meatus. If the main mass of the cerebral Skull is located in front of this line, then the Skull is called frontopetal, if behind—occipitopetal. The types of Skull are of great importance, since to these types correspond different types of its contents: e.g. in dolichocephals the base

of the Skull is elongated in length, accordingly there is a displacement of the openings for vessels and nerves. Malformations of the bones of the Skull are encountered quite often, but practical significance is mainly had by partial underdevelopment of the bones of the Skull, leading to the formation of so-called brain hernias; of other abnormalities of the cranial bones one should note aplasia crani, expressed in a lack of ossification of the cranial bones. The cause of such an anomaly is considered to be rickets. Treatment is reduced to intensified

Figure 11. Vessels and nerves of the occipital region: 1-m. occipitalis; 2-n. occipitalis major; 3-a. occipitalis; 4-n. occipitalis minor; 5-trunci posteriores nn. cervicalium; 6-m. trapezius; 7-m. sternocleidomastoideus; 8-m. splenius; 9-attachment of m. trapezius to linea nuchae sup.; 10-a. auricularis posterior.

nutrition of such children. The reverse and more important in all respects clinical form is premature ossification of the cranial bones, leading to insufficient capacity of the cavity of the Skull with subsequent cessation of brain development—microcephalus (see). Congenital clefts of the Skull cause hernial protrusions of the contents of the Skull through a defect in the cranial bones. There are anterior and posterior hernias. Anterior ones are located along the line connecting the facial bones with the cranial ones. Depending on the direction of the hernial canal, among anterior hernias are distinguished nasofrontal, nasoethmoidal and naso-orbital. Posterior hernias are located strictly along the median line of the Skull, above or below protuberantia occipitalis. Depending on the nature of the contents, hernias are divided into encephalocele, if the contents consist of brain substance, hydrencephalocele, when among the brain substance there is a cavity containing cerebrospinal fluid, and finally hydromeningocele, a hernia of the brain membranes alone, which contain brain fluid. It is believed that all these forms originate from encephalocystocele and represent only individual stages in the development of brain hernias. Clinically, anterior hernias manifest themselves as the presence of a tumor located around the root of the nose, at the inner or outer angle of the eye. The tumor usually does not reach the size of an orange; the skin coverings over it are either completely normal or thinned. The tumor is to some extent compressible. During straining the tumor tenses, increases in volume. Anterior brain hernias occur 3 times more often than posterior ones; posterior ones sometimes reach enormous sizes and usually have a pedicle. Brain hernias must be differentiated mainly from hemorrhages, blood tumors of newborns, dermoid cysts and angiomas. Location in the region of the parietal tubers, irreducibility, absence of a bony ridge speak for a blood tumor. Dermoid cysts are located exclusively at the fontanelles, where brain hernias never occur. It is difficult to distinguish anterior brain hernias from an angioma, however, location in the region of the sagittal suture, sometimes the presence of vascular murmurs, clearer pulsation help to distinguish an angioma. The course of brain hernias is always unfavorable: sooner or later their bearers are doomed to death. Conservative methods of treatment are now abandoned as not achieving the goal, however, even radical intervention does not give good results: Petrov in 146 cases subjected to operation, counts up to 40% mortality. Anterior hernias are especially unfavorable. The usual complication that kills the operated is purulent meningitis. The operative measure should consist first in removing the hernial contents and second in closing the defect. The first stage presents no difficulties, except when there is brain in the hernial sac, when removal is impossible. The defect is closed either only by the skin coverings or with the help of a bone-periosteal flap on a pedicle, taken from the neighboring region of the supraorbital arches, where the bone is quite thick, so there is no danger of opening the cranial cavity.

Injuries to the bones of the S. constitute an important chapter in clinical surgery, not only in themselves, but also due to the complications that so often accompany them. Usually, bruises of the bones of the S. are the result of external blunt trauma. The bruises themselves are not of great importance, but they are often accompanied by shock and intracranial hemorrhages. Usually, if only the soft tissues of the S. are bruised, there is a limited swelling in the area of the bruise, painful on pressure, or an accumulation of blood—a hematoma—which quickly resorbs under the influence of rest and cold. Bruises accompanied by concussion or hemorrhage proceed with cerebral phenomena: in the first case, with loss of consciousness that quickly passes without leaving consequences; in the second case, besides loss of consciousness, which can persist for a long time, they are accompanied by local focal phenomena: convulsions, pareses, paralyses, etc. Treatment in this case should consist of absolute rest, and if the phenomena intensify, of decompressive surgery. Bruises are often complicated by fractures of the bones. Wounds of the bones of the S. are encountered in practice quite often, especially during wartime. Wounds can be punctured, incised, or chopped. Anatomically, wounds are differentiated as linear or flap-like. One should also distinguish wounds that do not penetrate the cranial cavity (Figure 13. Lymphatic vessels and regional lymph. glands of the head: 1-lgl. occipitales; 2-lgl. auric, post.; 3-lgl. cervic. prof.; 4-truncus lymphaticus jugularis; 5-v. jugul. int.; 6--a. carotis comm.; 7-lgl. submaxill.; 8-lgl. auric, ant.) and wounds that do penetrate. The latter type of wound usually proceeds with complications. Bruised wounds are more common than incised wounds. They already have the character of a fracture with displacement of fragments, sometimes with their deep penetration into the cranial cavity. In wartime practice, gunshot wounds of the S. are most common; they can be divided into two main groups: those that do not penetrate the cranial cavity and those that do. The difference between them is very significant, because in the second case, complications immediately appear after the injury, sometimes absolutely fatal. These injuries deserve attention because usually up to 70% of such wounded die on the battlefield (Razumovsky). Non-penetrating injuries are treated like ordinary soft tissue injuries, taking into account the special conditions of the location of the galea aponeurotica, which in purulent processes predisposes to spread. The external appearance of gunshot injuries to the bones of the S. is very diverse. Several types of cranio-cerebral injuries are distinguished: injuries at close range, which due to hydrodynamic action break the S. and brain into pieces, and injuries at longer distances, in which two types of wounds are distinguished: a) so-called tangential wounds, more superficial, forming a groove in the S. and brain; b) so-called diametrical, piercing the S. and brain along one of the long diameters, resulting in either a through-and-through wound or a blind one. The wounded in the S. die in the initial period either from destruction of life-important centers or from concussion of the brain; in later periods—from inflammatory processes of the brain and its membranes. With tangential wounds, careful primary treatment is necessary with removal of fragments, foreign bodies, freshening of the bone, brain, and tissues, with tight closure, provided the wounded person arrives no later than 12 hours. In other cases—open method of treatment. For through-and-through wounds, there are two methods of treatment: conservative and surgical, with the advantage still being the latter, in which, if performed in the first 8-12 hours, bone fragments and foreign bodies are removed, preventing subsequent complications. Conservative treatment is indicated in cases of late arrival of the wounded without the presence of cerebral complications. With injuries to the S., the difference between the entrance and exit wounds is particularly pronounced: the entrance wound is round, of small size; the exit wound is of larger size, with damaged, cracked, crushed edges. The clinical picture of gunshot injuries to the bones of the S. is extremely diverse and highly varied in its manifestations. Sometimes all signs are expressed very weakly, and the wounded person instantly falls dead. Between these extremes, a whole range of intermediate degrees is observed. Fractures of the S. Fractures of the vault of the S. are more common than fractures of the base. According to Murney, this ratio is expressed as 77% and 23%, according to Dukhanin—as 87% and 13%. They can be the result of direct or indirect violence. In the first case, the fracture occurs at the site of the action of violence; with fractures from indirect violence, it is a matter of compression of the S., and its integrity is violated outside the points of application of force. Fractures are distinguished as complete and incomplete. In the first case, it is a fracture of the lamina vitrea, while the lamina externa remains undamaged, and in the second case, the fracture extends to both plates. Clinically, with incomplete fractures without cerebral phenomena, such a fracture can easily be mistaken for a bruise, and only an X-ray gives the true picture of the injury, which is why an X-ray should be taken for any bruise of the S. to prevent subsequent cerebral complications (epilepsy). From an anatomical point of view, fractures are divided into: a) linear, b) multiple, c) star-shaped, d) comminuted, e) depressed, and f) fractures with comminution. Complications that occur with fractures of the cranial vault manifest themselves primarily in intracranial hemorrhages and compressions. The clinical picture of fractures of the cranial vault is very diverse: sometimes it is expressed very weakly, and sometimes it ends in death on the spot. Local signs of the fracture consist in tenderness of a certain area of the cranial vault, in hemorrhage and bruises at the site of the fracture and in its nearest vicinity. On palpation, if the fracture is not complicated, one can feel a depression or protrusion of the fragment, and sometimes mobility of the fragment. With open fractures, the matter is simpler. General signs of fractures of the cranial vault come down to signs of severe injury: vomiting, rare tense pulse, convulsions, paralyses, incontinence of urine and feces, stertorous breathing, unequal dilation of the pupils, complete loss of consciousness. Treatment should consist, in case of incorrect position of fragments or signs of brain compression, in the surgical removal of fragments. With cracks without cerebral phenomena, treatment should be conservative—rest, cold to the head. The diagnosis is much more difficult to establish with fractures from indirect violence, when the application of force is in one place, and the fracture is on the other side; these are so-called contre-coup fractures. In these cases, there is a violation of the bone or rupture of a vessel, for example, the a. meningeae mediae, on the side opposite the blow. In this case, the phenomena from the brain side and X-ray examination should indicate the site of injury. With severe cerebral phenomena, surgical intervention is indicated according to focal phenomena. Fractures of the base of the S. in most cases represent a fairly typical clinical form. The line of fracture can go in longitudinal, transverse, diagonal, or ring-shaped directions. Displacement of fragments is usually insignificant. Clinically, a fracture of the base of the S. is characterized primarily by signs of severe injury and of a cerebral nature: the general severe condition of the victim, phenomena of bruise or compression of the brain, unconscious state, stertorous breathing, change in pulse. Bleeding from the nose, ear, and orbits is particularly important. Bleeding from the orbit is expressed in the appearance of subconjunctival ecchymoses. With fractures of the base of the S., the damage can affect only the bone, and in these cases we have the above-mentioned phenomena. Sometimes these fractures are complicated by rupture of the dura mater, as a result of which sometimes there is leakage of cerebrospinal fluid from the ear, nose, and even entry of air into the cranial cavity and ventricle due to pulsatory oscillations of the brain and suction of air into these cavities, which also often leads to infection and meningitis. Sometimes the rupture of the dura mater is valve-like, which sometimes closes, and sometimes with strong straining opens and leads to abundant discharge of fluid. The prognosis is extremely serious. Cases without complications are treated conservatively—rest, ice to the head. With complications by cerebral phenomena, some recommend surgical intervention, expressed in decompression. Spasokukotsky proposed for injuries to the S. to perform massive (500-600 cm³) bloodlettings, which give very rapid and reliable improvement in the general condition, disappearance of headache. Inflammatory diseases of the bones of the S. can be acute and chronic. Acute inflammatory processes here manifest as 1) acute periostitis, 2) acute osteomyelitis, and 3) acute inflammation of the veins of the cranial bones. The cause of acute periostitis is either trauma or direct spread of the process from the soft tissues or from the cranial cavity. Locally, there is a picture of either an abscess or a phlegmon. The swelling is usually of considerable size, but never crosses the boundary of attachment of the galea aponeurotica.

Prognosis is favorable.-Treatment is usual for acute purulent processes with counter-openings at the level of attachment of galea aponeurotica.-Acute osteomyelitis is either a direct transition of the inflammatory process from the periosteum or a manifestation of infectious osteomyelitis. Anatomically, it amounts to the necrosis of a certain area of bone with subsequent sequestration of the necrotized bone. A feature is that sometimes the process is not delimited and sequestration does not occur, therefore the course is prolonged; in these cases, treatment should be conservative, and operative only in cases of complete sequestration.-Inflammation of the veins of the cranial bones is a consequence of particularly severe purulent inflammation of the soft parts of the skull or as a complication of thrombosis with suppuration of the cerebral sinuses. Clinically, it proceeds with symptoms of general sepsis, with cerebral symptoms. Prognosis is poor. Among chronic inflammatory processes, tuberculosis occurs, which proceeds either in an infiltrative-progressive form with the formation of granulations, or as a sequestrating form with the formation of small sequestra, or as a perforating form when the entire thickness of the bone is destroyed. Clinically, tuberculosis of the cranial bones gives a particularly clear picture in cases where it leads to the formation of a cold abscess and subsequent fistulas.-Syphilis of the bones of the skull is quite common; according to some authors, gummatous lesions of the bones of the skull are observed in 19-20% of all bone manifestations of syphilis. All forms of bone lesions are encountered: osteitis, periostitis gummosa, sequestra, etc. A very characteristic feature is that in syphilis, along with destructive processes, the bone shows considerable regenerative abilities, as a result of which it acquires a very characteristic appearance: on the one hand, the bone appears eaten away, destroyed, and on the other hand, covered with bone outgrowths, tubercles, etc. Prognosis is generally favorable. Recognition of syphilis of the cranial bones is based on data characteristic of bone syphilis in general.-Actinomycosis of the cranial bones is rare. The clinical picture consists of signs of a chronically proceeding inflammatory lesion of the bones of the skull in the presence of a characteristic actinomycotic infiltrate in the soft tissues with its discharge. Treatment consists of operative and medicinal measures. Tumors of the bones of the skull are either primary, with their starting point being the bone itself, or secondary, with the tumor spreading to the bone from the coverings or from the contents of the skull. Among primary tumors, exostoses and osteomas are encountered; they grow slowly and do not cause particular subjective disorders; however, if they develop into the cranial cavity, they can cause cerebral symptoms. Cholesteatomas of the skull are more common in the temporal bone. A cholesteatoma is a tumor of pearly-white color, characteristic crumbly consistency, soft to the touch. Microscopically, masses of keratinized epidermis are found with an admixture of cholesterol crystals and fatty acids.-Special mention should be made of the cyst-like formations called sinus pericranii. By this name is meant a cystic formation containing venous blood. This formation lies between the bone and the periosteum and is connected with the contents of the skull. The etiology of this disease is unclear. Treatment is usually operative, but presents certain technical difficulties, as one has to deal with bleeding from the veins of the cranial bones. The most convenient method is to perform trepanation with ligation of the feeding vessels. However, cases have been described where bleeding was stopped by muscle tamponade. Among malignant tumors of the bones of the skull, cancer occurs, which is secondary. The lesion of the bones has a creeping character. Anatomically, it appears as a superficial ulcer with ragged edges and an uneven bottom. Sarcoma of the bones of the skull is either primary bone, actually originating from the bone, or secondary-as a result of the growth of a tumor from the cranial cavity or from the coverings. Round-cell and spindle-cell sarcomas, sarcomas of vascular and myxomatous structure are encountered. Sarcomas originating from the periosteum are of denser structure; sarcomas originating from the diploë are softer. Sarcomas developing from the bony part have the properties of osteosarcomas. Finally, myelogenous sarcomas occur; they have a capsule and are surrounded by proliferated periosteum. Clinically, it should be noted that sarcomas are of large size and have very little tendency to ulcerate. Treatment consists of operative intervention. Echinococci are rarely found in the bones of the skull. Cases of echinococcus of the temporal muscle, frontal muscle, frontal sinus, ethmoidal sinus have been observed. In all these cases, the matter leads to the erosion of the bone and the growth of the tumor into the cranial cavity. Treatment consists of removal of the CYST,