Herrick, Cranial Netves of the Cod Fish. 279 



length. Both AUis and Cole have described this nerve cor- 

 rectly. Not all of its twigs were traced to sense organs (the 

 skin being defective in places), but this is probably the mode 

 of ending of all of them, as this area of skin has an independ- 

 ent general cutaneous innervation. 



Following the nerve last described, branches are given off 

 from the hyomandibular trunk for the canal organs 10, 9 and 8 

 of the operculo-mandibular line, as figured by Cole. The next 

 nerves to leave the trunk are three fine fibered twigs which ap- 

 parently include all of the remaining general cutaneous fibers 

 of the trunk. These distribute to the skin of the ventro-ceph- 

 alic edge of the operculum. 



The trunk then enters the lower jaw and runs forward 

 along the inner side of Meckel's cartilage in the manner typi- 

 cal for teleosts. Unlike Menidia, however, the truncus here 

 appears to contain only lateralis fibers, i. e., it consists only of 

 the external mandibular nerve, the communis fibers constituting 

 the internal mandibular nerve not being present in this fish. The 

 nerve, as seen in cross sections, is composed of coarse and 

 medium fibers, the former scattered irregularly among the latter 

 and all very densely myelinated. There are a very few quite 

 small fibers among them, but these are not segregated into a 

 compact fascicle, as general cutaneous or communis fibers gen- 

 erally are when they accompany lateralis fibers^ and besides, 

 though small, they are heavily myelinated. 



The peripheral relations of the truncus hyomandibularis 

 have been carefully worked out. I find that they correspond 

 closely to Cole's descriptions, which I confirm in every impor- 

 tant respect. There would seem to be great individual varia- 

 bility as to the precise courses of the several nerve trunks run- 

 ning in the mandible, even on opposite sides of the same speci- 

 men. Yet these variations are of small morphological im- 

 portance. 



8. The Infra-Orbital Trunk. 



The truncus infra-orbitalis is composed about as in Meni- 

 dia. It breaks up into its component rami earlier in Gadus 



