XIII.] THE FROG. 183 



tongue, which it enters and then supplies that organ. 

 Moreover, it gives off muscular branches and a large 

 anastomotic branch to the seventh. 



10. 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-cutaneous artery, the 

 other (6) 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- 

 tinued back as a slender filament, the filum terminate, to the 

 commencement of the canal of the urostyle. The diameter 

 of the cord is. somewhat enlarged opposite the origin of the 



