CoGHiLL, Cranial Nerves of Amblystoma. 243 



dorso-trachealis. It then penetrates this muscle from the 

 antero- lateral to the postero-mesial side, and crosses the ante- 

 rior border of the m. cucullaris as the latter passes downward 

 across the pharynx. This variation occurs in the nerve of one 

 side only. 



The first ramus {vsc.i) of this trunk arises near the gang- 

 lion from the ventral and lateral portion of the nerve. It sends 

 fibers {vsc.ia.) directly to the muscle cucullaris, and also fibers 

 through this muscle to the m. dorso-trachealis. It will be re- 

 membered that the fourth root of the vagus, the axones of which 

 emerge from an ascending lateral tract in the cord and medulla, 

 enter the most ventral part of the t. visceralis. From this region 

 of the nerve, immediately outside the ganglion, the fibers go 

 out which innervate the m. cucullaris. In origin and distri- 

 bution, therefore, these fibers function as N. accessorius. 



The larger, fine fibered portion of the first branch, how- 

 ever, inclines laterad anteriorly of the m. cucullaris and con- 

 tinues caudad laterally of this muscle. Early in its course the 

 nerve gives a twig to the epithelium of the pharynx (not fig- 

 ured) ; later it sends a large number of fibers to the third and 

 fourth mm. levatores arcuum (not figured). From this nerve 

 there arises, also, a typical r. pre-trematicus (/;-/. Xj.) which 

 passes along the mesial side of the third epibranchial bar and 

 enters the third branchial arch. In one specimen, a small twig 

 from the second t. branchialis vagi, corresponding to the fifth 

 ramus of the glossopharyngeus, also entered this arch close to 

 the r. pre-trematicus. In this specimen, also, a twig from the 

 first ramus of the t. visceralis entered the fourth branchial arch, 

 corresponding in its distribution with the fifth ramus of the 

 glossopharyngeus. 



Near the m. levator arcus, this nerve sends a twig of small 

 fibers, probably communis, to the strip of epithelium which 

 joins the epithelium of the fourth branchial arch with that of 

 the pharynx. The larger, terminal portion of the nerve, how- 

 ever, passes between the fourth m. levator arcus branchii at its 

 insertion and the m. dorso-trachealis, then across the mesial 

 aspect of the caudal tip of the fourth epibranchial bar. From 



