FOURTH TRUNCUS BRANCHIALIS VAGI. 105 



{^. I. a. e.), the other passes from the post-trematic nerve 

 to the m. obliquus dorsalis {m. o. d.). 



The pre- and post-trematic nerves are as before, save 

 that at the base of their gill (the fourth) the remaining 

 motor fibres of the ventral ramulus supply the m. trans- 

 versus ventralis (one of the interarcuales ventrales) instead 

 of the m, obliquus ventralis, which does not appear in this 

 gill. The terminal sensory fibres of this ramulus supply 

 the enormous taste buds near the median line of the floor 

 of the mouth, those of the dorsal ramulus similar buds 

 farther laterally, as in the other gills, 



VI. — Fourth Truncus Branchialis Vagi. 



The fourth branchial (/. X. 4..') separates from the gen- 

 eral vagus complex farther caudad than any of its other 

 rami. As in the preceding cases, it draws off both coarse 

 and fine fibres. As it arches around dorsally from the 

 mesal to the lateral aspect of the m. obliquus dorsalis 

 posterior (of Vetter) it contributes most and probably all 

 of its coarse fibres for the innervation of this muscle 

 {in. 0. d. p.). 



This muscle, passing from the fourth gill bar to the caudal edge of 

 the lower pharyngeal bone and classed as one of the interarcuales 

 dorsales, is described by Vetter ('78, p. 509) as peculiar to Esox. 

 The relations in Menidia conform in general to his description, 

 though the muscle here seems to be larger and to arise mainly from 

 the fourth epibranchial instead of from the ceratobranchial, as in 

 Esox. 



The pre- and post-branchial rami are both very small. 

 The former passes to the fourth gill in the manner typical 

 for the other gills: the latter is very minute and composed 

 exclusively of fine, i. e., sensory fibres. There being no 

 gill behind the fifth gill cleft, it distributes to the general 

 mucosa dorsally of the beginning of the oesophagus and 



