Macrogria

MACROGRIA (from Greek makros- large and Latin gyrus- convolution), an abnormality in brain development characterized by the presence of abnormally wide convolutions; some authors use the term pachygyria to denote a brain with such convolutions. The etiology and pathogenesis of such brain malformations are not yet fully clear: they may be a congenital change or depend on secondary exogenous factors affecting the embryo's brain at various stages of its development. M. may also be observed in the brain of an adult as a result of excessive stretching of the convolutions by cerebrospinal fluid (hydrocephalus) or by neoplasms located under the cortex (for the etiology, pathogenesis, pathological anatomy, and clinic of these M.- see the respective articles). Macroscopically, the brain may be normal in size and weight or, conversely, very small (see Microcephaly), atrophied; its convolutions are very wide and normally convex; the number of sulci is very small (see fig.). As a rule, primary sulci exist and a small part of secondary ones, but there are no tertiary ones, due to which the brain is very poor in convolutions and resembles the brain of an embryo at the 6-7th month of intrauterine life. Upon microscopic examination of a macrogiric brain, no abnormalities in the structure of the cortex may be found; more often, deviations are encountered: embryological type of cortical structure, absence of proper differentiation of layers, alteration in the shape, size, and position of cortical cells, presence of a gray matter layer (Mittelschicht) in the white matter of the convolutions, as if separated from other layers. Clinically, M. may not manifest at all, but more often such subjects show a decrease in intelligence down to complete idiocy (see Microcephaly).

E. Kononova. MACROSCOPY (from Greek makros- large and scopeo- I look, I examine), macroscopic examination, or examination of various objects with the naked eye; it is opposed to microscopy, i.e., examination with the help of a microscope or magnifying glass. M. in clinical and pathological-anatomical practice constitutes the first and most important moment in objective examination. M. includes primarily the general, or so-called external examination of the object, whether it is an entire individual or a part of it (organ, tumor, etc.). The second stage of macroscopic examination will be a detailed examination of the object's details, e.g., during its dissection. General examination of the object is necessary for recognizing the general structure and form, e.g., the genus and species of the animal, the habitus of the subject, the color of the coverings; at this, the smells felt during examination, consistency, temperature, moisture, etc. are also recorded. Practically, both in the clinic and on the dissecting table, it can be firmly established that the said macroscopic examination of the 'whole,' performed systematically and with sufficient attention, in itself can already provide much, and conversely- insufficiency or neglect of such examination, a quick transition to the analysis of details, often only confuses the researcher and does not yield the desired results. The second stage in M.- the analysis of details of the same object- should either confirm the correctness of the assumptions already made in connection with the general examination and deepen them, or give new data, which may completely refute the said assumptions. Here, various macroscopic reactions are often used (e.g., reaction to amyloid, Pirquet reaction, phenomenon of blanching, Rumpel-Leede phenomenon, etc.). In pathological-anatomical practice, it is customary to verify all private macroscopic conclusions under the microscope whenever possible, and in forensic-medical practice, often chemically, micro-spectroscopically, etc. Experience shows that even with great observability, macroscopic diagnoses are often refuted microscopically; on the other hand, this is still no reason to ignore macroscopy: as a rule, the position remains valid that in the vast majority of cases, a macroscopic diagnosis of the disease is quite possible, and a significant part of the art in medical and pathological-anatomical research falls precisely on the ability to understand the visible without the help of microscopy, leaving the latter the role of a mandatory control instance (see also Biopsy, Autopsy, Diagnosis).-M. is a valuable method in the examination of various body fluids, secretions, and excretions. Thus, from M. of urine, one can to some degree judge the course of the gonorrheal process, from M. of sputum- the nature of pulmonary suffering, from M. of blood- of some of its diseases, from M. of vomit, gastric juice, feces- of diseases of the gastrointestinal tract and its glands. L«t.: Weisz E., Diagnostik mit freiem Auge-Ektoskopie, Berlin-Wien, 1924 (Russian edition- Ektoscopy- diagnosis with the naked eye, Berlin, 1925).