xiii.] THE FROG. 19 r 



this the trunk of the glossopharyngeal is given off. 

 It passes downwards and forwards to the root of the 

 tongue, which it enters and then supplies that organ. 

 Moreover, it gives off muscular branches and a large 

 anastomotic branch to the seventh. 



i o. The Pneumogastrici or Vagi. 



Immediately after leaving the ganglia these nerves 

 separate from the glossopharyngeal and each gives 

 off a cutaneous branch to the dorsal integument of 

 the head and trunk : it then divides into two 

 branches, one of which (a.) runs on the inner side of 

 and above the cutaneous branch of the pulmo-cuta- 

 neous artery, the other (b.) lies below and diverges 

 from the first. 



a. is the laryngeal nerve. It passes beneath the 



first cervical nerve, then crosses over the third 

 aortic arch and, about its middle, turns sharply 

 round it to be distributed to the larynx. This 

 nerve corresponds with the recurrent laryngeal 

 of the higher animals. 



b. is the splanchnic branch. It gives off (gastric) 



branches to the gullet and stomach, and a fine 

 nerve (cardiac) which passes beneath the pul- 

 monary artery and along the root of the lung to 

 the heart, and ends in ganglia situated in the 

 septum of the auricles. The splanchnic branch 

 finally enlarges and is distributed to the lungs 

 and stomach. 



The myelon or spinal cord is continued back from the 

 hind-brain as a subcylindrical cord, which lessens somewhat 

 rapidly towards its apparent end at the level of the seventh 

 vertebra. It does not really end here, however, but is con- 



