THE FROG. 99 



ventrally to form two cord-like tracts {ventral 

 roots of the olf. lobes), 



b. The lamina terminalis ; a median bilobed emi- 

 nence, interposed between the bases of the 

 hemispheres. 



c. The optic lobes ; seen to project laterally, be- 

 hind the hemispheres. 



d. The oJ)tic tracts ; band-like masses arising in 

 connection with c; that of the left side giving 

 off the optic nerve to the right eye and vice 

 versa. The interlacing of the two at the point 

 of decussation, to form the optic chiasma. 



e. Lying in the ventral middle line immediately 

 behind the optic chiasma there will be seen, in 

 the order named 



a. The tuber cinereum ; a large tongue-shaped 

 mass, bilobed posteriorly. 



y3. The itifiindibulum ; a small stalk-like body 

 giving attachment to 



y. the pituitary body ; a rounded pinkish mass 

 (highly vascular in the fresh state). 



iii. Examine from one side {lateral aspect), and com- 

 pare generally with i. and ii. 



iv. Slice away, with a small scalpel, the dorsal walls 

 of the cerebral hemispheres and olfactory and optic 

 lobes, and remove in like manner the greater por- 

 tion of the cerebellum and roof of the thalamen- 

 cephalon. The central cavities or ventricles will 

 thus be laid bare ; they can be resolved into two 

 sets, as under : 



7-3 



