Comparative Anatomy of the Brain. 581 



hind end, as well as divided by a longitudinal median fissure. So there 

 are four bulbs answering to the quadrigemina, the front ones, answering 

 to the nates, being much the largest. 



FIG. 292. Brain of Lizzard, top view. ( John Anderson.) 



O. Olfactory lobes. D. Cerebellum. 



A Cerebral hemispheres. E Fourth ventricle. 



C. Optic lobes. F. Spinal cord. 



The cerebral crura, in advance of the optic lobes, show 

 slight enlargements like optic thalami ; after passing which 

 the fibres of the crura pass into the hemispheres. The hem- 

 ispheres are hollow, and are separated by the thin wall be- 

 longing to each. Into each of their ventricles a corpus 

 striatum projects from the under and outer side. The sep- 

 tum between the two hemispheres is perforated for the pass- 

 age of a " choroid plexus." The ventricles are continued 

 forward into the olfactory lobes, which are very large. In 

 lizzards the optic lobes are relatively larger than in the 

 snakes, the eyes being correspondingly more active. They 

 constitute one pair, however, instead of two, and are hollow. In Tur- 

 tle ( Chelone ) the cerebellum is an arched body of equal thickness 

 throughout, covering the upper end of the ventricle. (Fig. 293.) The 

 rest of the ventricle is covered by a web of vascular matter derived 



FIG. 292. 



FIG. 293. 



FIG. 293. Side view of Brain of Turtle ( Chelone.) 



FIG. 294. Top view of same. 



P. Cerebrum . 



C. Cerebellum (in 294 it is raised to show the fourth ven- 



F. Fourth ventricle. [tricle.) 



O. Optic lobes. 



F. Ventricle in same. 



E. Olfactory lobes. 



S. nerves. 



k. Ventricle in olfactory lobes. 



X. Ventricle in cerebrum, containing corpus striatum and 

 communicating with ventricle in olfactory lobe. 



W. Space between O and P, covered by pineal gland. 



ra, m. Bristle, showing communication between optic 

 ventricle and fourth ventricle. 



a. Optic nerves. 



d. Swelling of same in passing over the crura cerebri. 



(John Anderson.) 



from the sides of the medulla oblongata. The 

 optic lobes are smooth and hollow, their ventri- p IGt 294. 



cles communicating with the third and fourth ventricles. The aqueduct 

 of sylvius lies below and between them. There is a pituitary gland be- 

 low the third ventricle and the pineal gland above. The crura cerebri 



