NEUROLOGY OF THE SAUROPSIDA. 



259 



J?-n. 



O^f-, 



I>n 



C7> 





Cb. 



XTinJu^^S 



OIJ^. 



jpy- 



Fig. 90. — A, C, the brain of a Lizard {Psammosaiirus Senffalensis), and B, D, of a bird 

 {Meleagris gallopavo^ the Turkey), drawn as if they were of equal lengths. A, B, 

 viewed from above ; C, D, from the left side. Olf.^ Olfactory lobes ; Pn.^ Pineal gland ; 

 Jimp., cerebral hemispheres ; J/&., optic lobes of the mid-brain ; C6., cerebellum ; 3f. 

 6>., medulla oblongata; *«., iv.^ vi., second, fourth, and sixth pairs of cerebral nerves; 

 Pi/., pituitary body. 



base of the brain, and are connected over the aqnceductus 

 Sylvii by a broad commissural band. 



Each prosencephalic lobe contains a lateral ventricle (con- 

 tinuous through the foramen of Munro with the third ven- 

 tricle), which is little more than a fissure between the very 

 thin inner wall of the lobe and its thick outer part, which con- 

 tains the corpus striatum. The corpora striata are united by 

 an anterior commissure, which is not of large size. The thin- 

 ning of the inner wall of the lobes, from the margin of the 

 foramen of Munro backward, which gives rise to the fissure 

 of Bichat in the 3IammaUa, extends for a very short distance 

 in the Sauropsida^ even in birds. 



The olfactory lobes are usually elongated, and contain ventri- 

 cles continuous with those of the prosencephalic hemispheres. 



In all Sauropsida the motor nerves of the tongue pass 

 through a foramen in the exoccif)ital bone. Hence, twelve 

 pairs of cranial nerves are present, except in the Ophidia^ 

 which possess no spinal accessory nerve. 



The lateral cutaneous branches so generally sent to the 

 trunk by the pneumogastric in the Ichthyopsida are absent, 

 but the pneumogastric gives a recurrent branch to the larynx. 

 The third, fourth, and sixth nerves arise quite independently 

 of the fifth. 



