5. Longitudinal Sinus. Character of walls and contents. Thrombosis, with purulent or gangrenous inflammation, is the most important condition. Note mouths of superior cerebral veins.
6. Meningeal Vessels. Note grooves, rupture, thrombosis, hemorrhage, infection, amount of blood, symmetry of distribution, etc. Traumatic rupture of middle meningeal is the most important condition.
7. Basal Vessels. Anomalies in size and distribution, thickness and character of vessel-walls (sclerosis, atheroma, aneurism, calcification). Thrombosis, embolism, aneurism, sclerosis, atheroma, calcification, obliterative endarteritis due to syphilis, are the most common conditions. The changes in the middle cerebral arteries are of especial importance in cases of apoplexy, softening, etc.
8. Inner Meninges. The arachnoid, subarachnoid space and pia are usually considered together. The arachnoid bridges over the sulci, the pia dipping down following the brain substance. The contents of the subarachnoideal space are best seen, therefore, between the convolutions. The inner meninges are gray, delicate and transparent; the pial veins show plainly, the arteries are empty and lie deeper, while the more superficial veins are uniformly filled with blood. Sclerotic arteries run more superficially and are more prominent. The removal of the skull-cap often gives rise to the presence of air-bubbles in the pial vessels, and this should not be mistaken for any pathologic condition. Hypostasis likewise should not be regarded as a pathologic condition. Normally the membranes are moist; in increased intracranial pressure (tumors, hydrocephalus, hemorrhages) they are dry and dull. Inflammation is shown by a loss of transparency of the membrane and by the presence of exudate in the subarachnoideal space. Old thickenings are white and opaque. The amount of fluid in the subarachnoideal space may be so great as to cause the arachnoid to bulge out over the sulci. Note character of exudate (purulent, fibrinous, serous or hemorrhagic). In purulent meningitis greenish-yellow or yellowish-white collections of thin pus are found in the meshes of the arachnoid; in fibrinous inflammation the exudate is grayish or milky white. The normal fluid (cerebrospinal) of the subarachnoideal space is clear and small in amount. It is increased in œdema and congestion, as well as in serous inflammations. In inflammatory conditions the membranes are dull and cloudy and the fluid more or less turbid. Pathologic adhesions may exist between dura and inner meninges, and between the latter and the brain-substance. In the latter case the meninges do not strip easily, but pull off portions of the cortex. Over tumors, gummata, areas of softening, the meninges may be so adherent that they cannot be separated from each other. In old syphilitics, alcoholics, cachexias of old age, etc., the pia may be thickened, white and opaque (leptomeningitis chronica fibrosa). Aneurisms of the pia vessels are of great importance in cases of meningeal hemorrhage. They may be very small (size of pea) and often are found only after very careful search. Atheroma, infective emboli, etc., are also causes of meningeal hemorrhage. Meningeal tubercles are very common and often hard to recognize. They are usually best seen over the basal meninges. Often they can be demonstrated by stripping off the meninges and floating the membrane in mercuric chloride or formalin fixing-fluids. After a few minutes’ fixation the tubercles appear as minute grayish or opaque points, the membrane often appearing as if sprinkled with fine sand or powder. The Pacchionian bodies of the arachnoid must not be mistaken for tubercles. They are grayish in color, and most abundant along the longitudinal sinus. The meninges over the two hemispheres should be compared as to transparency, thickness, blood-content, amount of fluid in arachnoideal space, etc.
The most important pathologic conditions of the inner meninges are anæmia, hyperæmia, stasis (asphyxia), œdema, hemorrhages (stasis, anthrax, aneurism, atheroma, infective emboli), serous, purulent and fibrinous inflammation (pyogenic cocci, bacillus pneumoniæ, pneumococcus, bac. coli, diplococcus intracellularis), chronic leptomeningitis (syphilis, alcoholism, toxæmia, etc.), tuberculosis, syphilis (gummatous meningitis), blastomycosis, actinomycosis and neoplasms. The last named are not common. Cholesteatoma, hæmangioma, lymphangioma, endothelioma, fibroma, osteoma and lipoma represent the benign tumors found here. Primary sarcoma is the most common tumor, usually angiosarcoma, perithelioma, cylindroma, round-cell-, spindle-cell- or myxosarcoma. Secondary sarcoma and carcinoma occur. Animal parasites are cysticercus and echinococcus.
8. Cerebrum. Weight of brain as a whole 1,200-1,400 grms. (15-50th year). Cerebrum averages 1,039 grms. in the female, 1,155 grms. in the male. A weight of 1,100 grms. may be taken as the minimum normal, and 1,700 grms. as the maximum for the brain as a whole. The relation of the brain-weight to that of the body is 2-100. In old age there is a loss of weight. Sagittal diameter 15-17 cm., transverse 14, vertical 12.5 cm.
Examine the convexity, comparing hemispheres, noting convolutions and sulci (size, number, symmetry, etc.) Atrophy of the gyri is shown by increased width of sulci and the narrower, sharper gyral apex. With increased intracerebral pressure the gyri are flattened and broader, and the sulci smaller. Note color and consistence of cortex, adhesions with pia, areas of fluctuation, induration, depressions, yellow softening, recent and old hemorrhages, effects of trauma, tumors, tubercles, gummata, etc. Examine median surfaces, note arching of corpus callosum. On section of the brain note color (pale in anæmia, red in capillary hyperæmia; hemorrhages, areas of softening, tumors, tubercles, gummata, sclerotic areas, abscesses, etc., all show color variation from the normal gray or white); consistence (soft in degeneration and abscess, hard in sclerosis), moisture (normally is moist-shining; moisture increased in œdema, inflammation, abscesses, soft tumors, recent degenerations; dry in old caseous tubercles and gummata, and in anæmia), blood-content (number of bleeding-points, distinguish from punctate hemorrhages), character of cut surface (normally smooth, sclerotic areas, abscesses and areas of softening are uneven and depressed, hard tumors and sclerotic blood-vessels are elevated above the surface). The absolute and relative size of cortex and medulla, and the distinctness of the boundary between them, should be noted.
Hemorrhages may occur in any part of the brain, and may be large or small. Rupture into a ventricle is always fatal. The large hemorrhages are due to rupture of a diseased artery; small punctate hemorrhages throughout cortex are usually embolic (fatty embolism). Old hemorrhages are brownish in color (pigment). Areas of softening are usually the result of embolism, thrombosis or sclerosis. They are usually yellow, yellowish-white or brownish-yellow or red.
9. Ventricles. Contain about a teaspoonful of clear fluid. This may become purulent, cloudy, hemorrhagic, fibrinous. Note size of ventricles and horns. (Fluid increased and ventricles dilated in hydrocephalus.) Character of ependyma normally gray-red, delicate; may be pale or red, indurated, thickened, roughened (chronic ependymitis), hemorrhagic, etc. Compare floors of lateral ventricles as to symmetry (corpus striatum large in hemorrhages), color, etc. Adhesions are found most frequently in posterior horns. A fine granulation of the ependyma is caused by miliary tubercles. Large solitary tubercles may be found in the ventricles. Do not mistake postmortem softening of ependyma for pathologic changes. In the third ventricle note the presence of any abnormal contents, character of wall, symmetry of corpora quadrigemina, etc. Look for same changes in fourth ventricle as in lateral. Lining is gray-white and delicate; floor should be gray-white, firm, and show anatomic structures. Gray sclerotic areas are often present in floor. Solitary tubercles, tumors (glioma, neuroepithelioma, gliosarcoma, sarcoma), dermoids and cysticercus-cysts may be found here. Examine aqueduct of Sylvius for abnormal contents.
10. Chorioid Plexus. The tela chorioidea is normally delicate and translucent. Note color (red, pale, cloudy), swelling, purulent infiltration, condition of blood-vessels, tubercles, etc. Psammoma, sarcoma, papillary epithelioma, carcinoma, fibroma, angioma, cholesteatoma, cysticercus and echinococcus may be found in the tela and plexus. Cysts due to œdema are very common, also aneurismal dilatations of the vessels. In cases of hydrocephalus the veins of Galen should be examined for thrombi or compression from without. In acute hydrocephalus the plexus is deep red; hyperæmic, its vessels distended with blood.