CoGHiLL, Cranial Neives of Aniblystoma. 239 



maticus of the second t. branchialis vagi. A motor branch (not 

 figured) passes from the main nerve to the second m. levator 

 arcus branchii. 



One of the three branches formed near the distal end of the 

 •first epibranchial bar is the fifth I'ajmis (JT, ibr.j), which descends 

 into the first external gill, innervates the m. levator branchii 

 and the m. adductor branchii, and receives the sixth ramus of 

 the glossopharyngeus. In the distal portion of the external gill 

 the nerve follows closely the large blood vessels, to which a 

 large number of its fibers seem to be distributed. 



At this same point of brancing, ^ sixth ramus {X,ibr:6), 

 also, passes caudad to anastomose with the third ramus of the 

 second t. branchialis vagi. It corresponds to the sixth ramus 

 of the glossopharyngeus and is probably a general cutaneous 

 nerve. 



As the branchial trunk turns cephalad into the gill arch, it 

 sends a motor brancii {X,ibr.f) to the second m. depressor 

 branchii, and beyond this becomes the r. post-trematicus {pst. 

 X,i) which is motor and communis in function. It assumes a 

 position laterally of the ventral margin of the second epibranch- 

 ial bar. Soon after entering the arch, the nerve sends a twio- 

 [X,ibr.8) to the pharyngeal side of the bar. The r. post-tre- 

 maticus then continues cephalad to the region of the m. inter- 

 branchiales, to which it sends a motor twig {X,ibr.io). In the 

 region of this muscle there is also a twig {X, ibr.g) which pass- 

 es across the lateral aspect of the cartilage to the epithelium of 

 the bar. A little further cephalad the nerve divides into two 

 terminal twigs, one of which ascends on the lateral and the 

 other on the mesial side of the bar to the epithelium covering 

 the proximal portion of the second branchial arch. 



J. — The Second Trmicns BrancJiialis Vagi. 



The second branchial trunk {X, Br. 2) of the vagus leaves 

 the ganglion just posteriorly of the first trunk, or fused with the 

 latter for a short distance. It inclines more caudad than the 

 first, across the ventral side of the third m. levator arcus 

 branchii, then caudad subcutaneously to enter the third branch- 

 ial arch. 



