Auatomit'al t'liaui 



649 



bulging- of the pituitary body and the optic recess is usually en- 

 larged. In severe cases the middle portions of the optic thai- 

 ami, the optic decussation and both the optic tracts appear to 

 be flattened. The portion of the epiphysis above and in front 

 of the conarium is sometimes dilated. 



On the medial surface of the occipital lobes there is a tri- 

 ang-ular protrusion, the size of which depends upon the extent 

 of the disease; this protrusion generally shows normal convo- 

 lutions (Fig. 88a). The depressions appear shallowest where 

 the two prominences are in contact. The enlargement of the oc- 

 cipital lobes already mentioned exerts pressure in proportion 

 to the enlargement in the backward direction on the corpora 

 quadrigemina, forcing the anterior pair apart, and presses tliem 

 against the base of the 

 brain. The enlarged oc- 

 cipital lobes also exert 

 pressure with their 

 lateral surfaces on the 

 corpora quadrigemina 

 towards the middle line, 

 thus flattening them and 

 forming a saddlelike de- 

 pression on the anterior 

 pair (Fig. 88b). 



The aqueduct ap- 

 pears to be reduced in 

 caliber not only on ac- 

 count of the compres- 

 sion of the posterior 

 part of the third ven- 

 tricle, but also owing to 

 the pressure by the cor- 

 pora quadrigemina, with 

 out there being any ad- 

 hesion of its walls. The 

 cerebellum is pushed 

 further back, the surface 

 of the crura cerebri is 

 smooth and not cordlike, 

 the oculomotor nerve 



appears to run a longer course and is pressed flat (Fig. 89). The 

 anterior border of the pons is sometimes curved in the upward 

 direction. 



In a portion of cases there is gelatinous infiltration of the 

 venous plexuses, formation of cysts with delicate walls, clioles- 

 teatomata* and thickening of the ependyma. 



In an acute relapse there are small hemorrhages under the 

 epend^^na, and there may be even centers of softening. The 

 ventricles frequently contain a turbid liquid which in some cases 



*See footnote, page 656- 



Fig. 89. Chronic liydroceplialu^ interims. View 

 of the base of the' brain shown in fig. 88. a. 

 Optic chiasma. b. Corpn^ nianiillare, forced 

 backwards, wrinkled and showing a depression, 

 c. Crus cerebri elongated and flattened and 

 sliowing an oblique furrow, d. Oculo-niotor 

 nerve, flattened and stretched, e. Pons Varolii, 

 wider than normal and Avith its anterior border 

 curving forwards. 



