Anatomical Preparations

ANATOMICAL PREPARATIONS (from Latin praeparo—I prepare), all types of visual aids, the material for the manufacture of which consists of actual tissues, organs, and parts of the organism of humans and animals. Anatomical preparations are microscopic and macroscopic. For microscopic preparations, see Histological technique, Microscopic technique, Photomicrography. The main requirements for macroscopic anatomical preparations are demonstrativeness and the possibility of storing them for an indefinitely long time in a state close to their natural appearance. A large number of different methods and their modifications have been proposed for the preservation of anatomical preparations. Each method includes a number of phases, the main ones of which are: 1. Preparation of the object (this includes dissection, making sections, removal of excess tissues, etc.). 2. Processing of the object with various chemical substances or mixtures thereof for the purpose of fixation, restoration of natural color, staining of tissues, etc. 3. Final mounting of the preparation. This includes enclosing in jars with preserving liquids, or in hermetically sealed glass chambers. Sometimes the preparation is dried directly, as, for example, bones, calculi, corrosion preparations, etc. The choice of the method for manufacturing a preparation depends on: 1) the goals and purpose of the given preparation; 2) the nature of the object of study, and 3) the method of further processing and storage of the preparation. The simplest and cheapest method is enclosing objects in 5-10% formalin or alcohol after preliminary fixation with the same liquids. A significant drawback of formalin storage is the browning of tissues in it, especially those rich in blood, due to the conversion of blood hemoglobin into methemoglobin. Therefore, formalin should be used only in cases where the goal of preserving the natural color in the preparation is not pursued, or when preserving anemic objects (malformations, embryos, gangrene of the lungs, etc.). The disadvantages of storage in alcohol are the discoloration and wrinkling of tissues (rich in water). Alcohol is used mainly for the preservation of small animals. Maceration (see) and drying are simple methods. They are used in the manufacture of bone preparations and in the storage of calculi. For the manufacture of bone preparations, the latter, having been previously freed from soft tissues, are subjected to soaking in water, the temperature of which is maintained at about 40-45°C all the time, and they are kept (changing the water several times) until the complete separation (rotting away) of the soft parts. Usually, this takes about 3-4 weeks. Then the bones are immersed in a warm 5-10% soda solution, dried, and degreased with benzine or ether (better in special devices). The degreased bones are dried again and bleached either in the sun with constant watering or by repeated immersion in a 1-2% solution of sodium peroxide, followed by washing and drying. The best bones are obtained when processing young and lean subjects. To disassemble a skull along the sutures, its cavity is stuffed with dry peas, the occipital foramen is plugged with a small piece of wood so that the peas do not spill out, and the skull is immersed in water. The peas, swelling, break the skull along the sutures. Senile skulls are not suitable for disassembly. More complex methods include: 1) injection, 2) clearing, 3) corrosion, 4) staining, and 5) preservation of the natural color of organs. The injection method is used in cases where it is desirable to reveal the circulatory or lymphatic system, glandular ducts, etc., in the preparation. (See Blood vessels, methods of investigation of blood vessels, Lymphatic system, lymphatic vessels, Gerota method, Lungs, lung infections, Liver.) The injection method is often used in combination with dissection, clearing, and corrosion. When choosing an injection method, one should take into account the size of the object, the state of the tissues, and the method of further processing and storage of the preparation in order to avoid rupture of the injected system or dissolution of the mass during subsequent processing of the object. Clearing method. This includes such processing of tissues, organs, and sometimes the entire organism (animal), in which the object being studied becomes transparent. Most often, this method is used in combination with vessel injection. This method is based on the use of acids or alkalis or on impregnating the preparation with liquids whose refractive index is equal to the refractive index of the tissues being cleared. The greatest merits in the clearing technique belong to Spalteholz (see Spalteholz method). The basis of clearing with acids and alkalis lies in the ability of soft tissues, primarily connective and muscular, to swell, bind water, and turn into a gelatinous mass under the influence of acid and hydroxyl ions. The clearing properties of acids have found application in the preparation of preparations of the peripheral nervous system. Clearing in these cases is carried out to certain limits (monitoring the delineation of nerve fibers and ganglia), because with prolonged action of the acid, tissue melting occurs. Of the acids, the most commonly used are acetic and formic (from 0.5% to 3%), depending on the time and the object. Storage of such preparations is carried out in 20-30% alcohol or in formalin. The clearing properties of alkalis have found application in the Schultze method (1897) for determining the ossification points of a fetus. The corrosion method was first applied in 1672 by the Leiden physician Jan Swammerdam. Later developed and described by Hyrtl. - See Blood vessels, methods of anatomical investigation of blood vessels. The staining method aims at contrast color differentiation of various elements of the animal organism. Carmine, hematoxylin, Methylene blue, Fuchsin, Eosin, and metal salts, e.g., gold, silver, are used as "dyes." The effect of tissue staining is the result of a complex interaction between the dye and the tissues being stained. The very process of staining has been studied very incompletely and fragmentarily. The method of staining macroscopic and microscopic sizes was introduced recently and developed mainly by V. Vorobyov and his students. The most common is the staining of the nervous system (autonomic nervous system, partly peripheral spinal nerves and the brain). Staining of internal organs is in the development stage and has been worked out for some of them (trachea, stomach, intestine, urinary bladder, gallbladder). For an example, we will cite some stains. Staining with osmium is performed by smearing the nerve (with a glass rod) with a 1% solution of osmic acid. As staining proceeds, the nerve is dissected and the staining continues further. When staining the nerves of internal hollow organs with gold, the organ is washed, placed in a weak solution (0.5%) of formic acid until light clearing, and then in a gold solution (faint straw color), which is later reduced in weak solutions of Methylene blue or in infusions of lemon or orange peel. The preparations are stored either in glycerin or they can be processed according to Spalteholz. Staining with Methylene blue requires preliminary washing of the preparation with plain or distilled water, depending on the staining method. The preparation is injected with a 0.5-0.02% solution of Methylene blue (depending on the method), after which the preparation is removed from the cadaver and immersed in a weak solution of the same dye. Methods of staining with Methylene blue are divided into methods suitable for cadaveric material and methods for so-called vital staining. It should be noted that not all organs stain equally, and therefore, for proper staining, a specific methodology is developed for each organ. In the manufacture of pathological-anatomical preparations, methods for preserving the natural color of organs are widely used. Here, it concerns mainly the preservation of the color of the coloring matter of blood and fat. Therefore, objects should not come into contact with water before the processing process, as it causes hemolysis. The essence of many methods consists of sequential exposure to formalin, alcohol, and glycerin. In formalin, blood hemoglobin is converted into methemoglobin, which causes the organ to take on a dirty brown color. Subsequent treatment with alcohol converts methemoglobin into its red modification-kathemoglobin. The diffusion capacity of formalin can be enhanced by various additives to the formalin solution, among which the artificial Carlsbad salt proposed by Pick is the cheapest, and the acetic acid salt indicated by Kaiserling is the most reliable. The addition of salt to a hypotonic formalin solution also prevents the leaching of erythrocytes by it. Prolonged stay of the object in alcohol leads to the destruction of the coloring matter (discoloration occurs) and the dissolution of fat. Therefore, for permanent storage, the preparation is transferred to glycerin diluted with a solution of potassium acetate; from the action of pure glycerin, the preparation would become too transparent. For recipes of salt formalin and glycerin, see Kaiserling method. According to Melnikov-Razvedenkov, for solution I, take: formalin 100 cm³, potassium chloride 5 g, potassium acetate 30 g, water 1,000 cm³. For solution III: glycerin 600 cm³, potassium acetate 400 g, water 1,000 cm³.

According to Pick I: 50 cm³ of formalin, 50 g of (artificial) Carlsbad salt, 1000 cm³ of water. Solution III - Kaiserling III. In solution I, objects remain, depending on their size, from 1 to 2 days, maximum 3 weeks, until they are completely fixed. The criterion for completed fixation is that no red blood should flow out of the vessels when compressed. For small objects, it is better to use strong solutions. For larger ones, such as the liver or brain, in order to ensure more successful penetration of the fixing liquid into them, one should take solutions with a formalin content of no more than 5-8%. In some cases, when it is important to preserve only the external appearance of the preparation, one can scoop out part of the unfixed mass from an incision made through the fixed surface layer. If only the surface of the cut plays a role, then one is content with a piece cut from the organ in the form of a plate. When placing the preparation into the fixing liquid, it is given the position in which one wishes to preserve it. For example, a segment of the intestine is attached with pins to a small board, which is then overturned so that the preparation ends up immersed in the fixing liquid. Tubular parts of organs are either opened and secured in such a position or stuffed with cotton wool. In order for the fixing liquid to have access to the preparation from all sides, cotton wool, etc., is placed under it. After the treatment with solution I is finished, the preparation is washed in water, dried slightly, and immersed in alcohol (96-97°). The preparation is left in alcohol until it regains its former color (if possible, not for long!). Depending on the size of the object, this period ranges from 1/2 hour to 12 hours. The time spent in solution III (glycerin mixture) is not limited. Due to the alcohol brought in with the preparation, solution III becomes cloudy, therefore it must be replaced with fresh solution at least once. In addition to the methods described above, based on the use of alcohol as a restorer of the natural color of the organ, there are other methods of preserving natural color without the use of alcohol. They are based on the formation of a stable bright red hemochromogen from hemoglobin under the influence of chloral hydrate added to solution I. With these methods, phase II (passing through alcohol) is omitted, and the preparation from solution I (with chloral hydrate) after thorough washing in water (6 hours) goes into Kaiserling's solution III. Jores recommends adding 50 cm³ of a saturated solution of chloral hydrate in distilled water to 1000 cm³ of the original Pick solution for solution I. Passing through alcohol is also omitted when treating the preparation with illuminating gas or pure carbon monoxide, which results in the formation of bright red and well-preserved CO-hemoglobin. According to the Schultz method, illuminating gas is passed through Kaiserling's liquid I for 1 hour before placing the organ in it, then the organ is placed in it for fixation, and a little more gas is passed through. After fixation in the carbonated liquid, the organ is washed in water and embedded in Kaiserling's liquid III. According to Kerner, organs and parts of them are subjected to the action of carbon monoxide before fixation, obtained from sulfuric acid by adding formic acid dropwise to it; after this, fixation follows in Kaiserling's liquid I or Melnikov-Razvedenkov's liquid, washing in water, and embedding in liquid III or in gelatin-agar-agar according to Talalaev. Storage of preparations with preservation of the natural color of the organ is carried out in rectangular glass jars. As a preserving liquid, solution III (pure) is taken. Besides that, preparations can be stored in the form of plates enclosed between 2 glasses. Shorr proposed a method of storage in hermetically sealed glass chambers without liquid. Great difficulties are encountered in preserving uric acid and urate salts (e.g., when preserving uric acid infarcts of newborns or gouty processes, as well as small lime deposits) due to the presence of formic acid in commercial formalin, which dissolves these salts. Therefore, it is easiest to fix and store such objects in 96° alcohol, or, after fixing in alcohol, transfer them to pure glycerin or embed them in gelatin. When finally sealing the preparations in jars, they are lowered directly or attached with silk threads to glass plates (it is convenient to use colored glass - milky, green, etc.). For greater demonstrativeness of various pathological channels, openings, and fistulas, glass rods are inserted into them. If one wishes to secure concretions present in an opened cavity, they are pre-dried and then glued with gelatin (after the gelatin has hardened, it is treated with 10% formalin to prevent its subsequent dissolution). Gelatin can also be used for sticking labels with inscriptions and numbers onto tissues. If an organ has a tendency to float (e.g., a lung), it is secured either to a glass plate or with glass rods. Jars with preparations mounted in this way are closed with glass plates (the edges of the plates should not protrude). Mendeleev's cement is used for sealing (125 parts of yellow wax, 500 parts of rosin, 200 parts of calcined mummy, and 3-5 parts of linseed oil; boil until the foam disappears). Sometimes mold grows in preparations stored in a glycerin mixture (which is possible with careless technique); then the jar must be opened, the preparation placed in formalin for a short time, and then enclosed in a new jar with fresh solution III. Recently, the Roentgen method has been used to study both normal and pathological anatomy. It has acquired particularly great importance in topographic anatomy. By filling vessels and other tubular systems with a contrast agent for this purpose, one obtains the finest images of these systems in the whole organism or in its individual parts. In pathological anatomy, X-rays from a corpse subject to autopsy can often reveal processes where they were least suspected, e.g., in the bones. If the altered organ is known, then the use of X-rays can facilitate the diagnosis of the localization and spread of the process. In the latter respect, the methodology proposed by Dr. Frank-Kamenetsky and developed by him together with Dr. Shlapobersky deserves attention. The mentioned authors obtained beautiful preparation-images of various, mainly tumor, processes by previously subjecting the object to treatment with a contrast liquid. This liquid was composed on the principle of brightly colored dyes used in histology, with the only difference that instead of an organic dye, an inorganic salt bound with a mordant was taken; when such preparations were transilluminated, parts of the preparation rich in chromatin substance gave contrast shadows. The methodology of this method is as follows: 1) fixation of the object under study in formalin (the preparation should have, if possible, the same thickness; when examining massive organs, e.g., the mammary gland, a plate-like section no thicker than 1 cm is made); 2) washing the object in running water (1/2-1 hour); 3) immersion of the object in a liquid of the following composition: Na-trii bromati 500.0, Liq. Ferri sesquichlorati 40.0, Acidi muriatici puri 10.0, Spiritus vini rectif., Aquae destillatae aa 725.0 (the finished solution has a dark brown color and can be used many times). After X-raying, the preparation is washed with water (1/2-1 hour) and remains suitable for microscopic examination. Particularly demonstrative preparation-images are obtained when studying tumors of the stomach, mammary gland, and some others.

The manufacture of anatomical preparations is carried out in various scientific institutes, mainly at departments of descriptive, topographic, and pathological anatomy, as well as at hospital prosectoriums, in surgical departments, and zoological cabinets. A large place in terms of the manufacture of anatomical preparations in recent years is occupied by the Central Scientific Research Institute of Visual and Educational Aids in Medicine, Biology, and Sanitary Culture (see Visual method). The manufacture of anatomical preparations requires, in addition to knowledge of museum work, also knowledge of normal and pathological anatomy, which is why it should be carried out either by doctors or by specially trained museum preparators, in the latter case necessarily under the guidance and control of a doctor. The most important purpose of anatomical preparations is their use as a visual aid in the study and teaching of relevant disciplines in universities, technical schools, and secondary schools. Anatomical preparations have become widely used in our country for sanitary education. Histological preparations - see Histological technique.

A. Kestner.