132 The Alligator and Its Allies 



Brain 



The cervical cord passes insensibly into the 

 medulla, the dorsal fiUTOw becoming wider and 

 more shallow as it merges into the fourth ventricle. 



A dorsal view of the brain is shown in Figtire 30, 

 A. The most prominent structures here seen are 

 the cerebral hemispheres, VH, whose combined 

 transverse diameter is greater than their longi- 

 tudinal. The tapering, cephaHc end of each hemi- 

 sphere forms an olfactory tract, I, which extends 

 ccphalad to form the olfactory bulb, B. ol. Lying 

 between the caudal ends of the hemispheres is a 

 small conical body, G.p., called by Bronn and 

 others the pineal body. The writer has found (62), 

 however, that this body is the paraphysis rather 

 than the epiphysis. Caudad to the ccrebra- 

 hemispheres and in contact with them are the 

 optic lobes, MH; they have about the same 

 shape and position as in the frog, but are much 

 smaller in proportion to the size of the hemispheres. 

 Immediately caudad to the optic lobes is the cere- 

 bellum, HH, somewhat elliptical in outline as seen 

 from above. 



Extending caudad from beneath the cere' ellum 

 is the medulla, NH, with its triangular fourth 

 ventricle. The outlines of the medulla are some- 

 what obscured by the numerous roots of the 

 eighth to eleventh cranial nerves, VIII-XI, which 

 arise along its dorsal border. The medulla, as was 



