NERVOUS SYSTEM. 



667 



wanting. There are thus only four metatarsals and digits. Each digit 

 has four phalanges. 



Nervoits System. 

 The brain has the usual five parts — cerebral hemispheres, 

 optic thalami, optic lobes, cerebellum, and medulla oblongata, 

 but the cerebral hemispheres cover the next two parts, and 

 the cerebellum conceals the medulla. Of the brain mem- 

 branes, the dura mater lines the cranial cavity, projecting 

 longitudinally between the cerebral hemispheres, and trans- 

 versely between the latter and the cerebellum, while the 



Fig. 236. — Under surface of 

 Rabbit's brain. (After Krause.) 



olf.L, Olfactory lobes ; o.t., olfactory 

 tract ;yi/., frontal lobe ; ch., optic chiasma ; 

 t.c, infaadibulum ; c.vi. corpus mammil- 

 lare ; 3, root of oculomotor ; 4, root of 

 pathetic ; 5, root of trigeminal ; 6, root of 

 abducens ; 7-8, roots of facial and auditory ; 

 /■■/., flocculi of cerebellum ; //., 12th or 

 hypoglossal nerve ; 10, roots of vagus ; 9, 

 the line runs in front of the root of the 

 glossopharyngeal to the root of 6 ; p.v., 

 pons Varolii ; tj., temporal lobe. 



vascular pia mater invests the brain closely. There are the 

 usual twelve pairs of cranial nerves. The spinal cord gives 

 off the usual spinal nerves, and there is a sympathetic system 

 as in most other Vertebrates. 



Fig. 235. — Dorsal view of 

 Rabbit's brain, with most of 

 cerebellum cut away. (After 

 Krause.) 



olf.L, Olfactory lobes ; c.Ji., 

 cerebral hemispheres ; o.L, optic 

 lobes; 4.1'., fourth ventricle (ex- 

 posed); s.c, spinal cord; 10, root 

 of vagus; Cb.y lobe of cerebellum. 



