CENTRAL NERVOUS SYSTEM OF ARMADILLO. 2Q I 



roofed over by a thin membrane. The greatest part of the 

 medulla oblongata is covered over by the cerebellum. 



The pons Varolii (PI. XXIV., Fig. 3, Pans] forms the most an- 

 terior part of the hind brain. It is a pair of slight elevations on the 

 ventral surface of the brain, a little posterior to the infundibulum. 



From the medulla oblongata arise all the remainder of the 

 cranial nerves, from the V to the XII inclusive. 



The V, or trigeininal nerve (PI. XXIV., Fig. I, V) arises from 

 the pons Varolii. It soon divides into two branches, the most 

 lateral of which subdivides again. 



The VI, or abducent nerve (PI. XXIV., Fig. I, VI] arises in 

 the region of the pons Varolii, and runs to the external rectus 

 eye muscle. 



The VII, or facial nerve (PI. XXIV., Fig. I, VII) arises in 

 close connection with the VIII nerve, in the region just laterad 

 of the pons Varolii. It soon subdivides into branches. 



The VIII, or auditory nerve (PI. XXIV., Fig. I, VIII) arises 

 with the VII nerve from the same part of the brain. It runs 

 directly outwards and enters the cochlea of the ear. 



The IX, or glosso-pharyngeal nerve (PI. XXIV., Fig. i, /A") 

 arises by several roots, from the ventral surface of the medulla. 



The A", or pneumogastric nerve (PI. XXIV., Fig. i, A") arises 

 by several roots from the medulla, just posterior to the IX nerve. 



The XI, or spinal accessory nerve (PI. XXIV., Fig. i, XI) 

 arises by several roots from the ventral surface of the medulla 

 and the spinal cord. Some of its roots arise from the spinal cord, 

 as far back as the fourth cervical nerve. 



The XII, or hypoglossal nerve (PI. XXIV., Fig. i, XII) arises 

 by several roots from the medulla oblongata, just posterior to the 

 origin of the XI nerve. 



2. SPINAL CORD. 



The spinal cord is cylindrical, but somewhat flattened dorso- 

 ventrally. In the cervical and sacral regions, it has a slight 

 enlargement from which the nerves of the brachial and lumbo- 

 sacral plexuses are given off. In the sacral region the cord 

 breaks up into a number of fine nerves which occupy the verte- 

 bral canal as the cauda equina. These nerve branches pass out, 



