THE RABBIT. 251 



close beside, and ventral to, the spinal column. The 

 ganglia are connected with one another, and with the roots 

 of the spinal nerves, by commissural nerves. These are 

 very difficult of dissection. 



Removal of the Brain. Cut away the top of the cra- 

 nium, and expose the brain fully. The elongate oval 

 olfactory lobes at its anterior end will be conspicuous. 

 Cut these off as far forward as possible, and gently lift the 

 brain out of the cranial cavity, on a thin, narrow blade of 

 metal, watching closely, and severing the roots of the 

 cranial nerves as fast as they appear, leaving as great a 

 portion of each as possible attached to the brain. Twelve 

 pairs of cranial nerves should be found during this oper- 

 ation. Proceeding from the front, these are : 



1. The olfactory nerves, the roots of which were cut 

 off at the anterior end of the olfactory lobes of the 

 brain. 



2. The optic nerves, large and conspicuous, at first 

 diverging but little, as they extend forward from their 

 point of crossing on the median ventral line. 



3. Two pairs of slender nerves, Appearing behind the 

 crossing of the optic nerves. 



4. The trigeminal nerves, very large and conspicuous, 

 arising a little farther back, and a little more remote from 

 the median ventral line. 



5. Two pairs of slender nerves, close behind the tri- 

 geminal, the anterior pair somewhat nearer the median 

 line. 



6. The auditory nerves, which are large, and which 

 arise a short distance behind the trigeminal, but farther 

 from the median line. 



7. Two pairs of rather small nerves, which arise close 

 behind, and a little above, the auditory nerves. The 

 larger pair of these are the vagus nerves. 



