144 NERVE COMPONENTS OF BONV FISHES. 



laris runs down its caudal and ectal side, while the com- 

 munis component runs down the cephalic and ental face 

 of the truncus, the two fine-fibred portions being separated 

 through the whole length of the truncus by the coarser 

 lateralis and motor fibres. It is only at the extreme ven- 

 tral end of the truncus that there is any possibility of any 

 considerable intermingling of their fibres. Here, though 

 the two fine-fibred components lie rather close together, 

 yet the sections show plainly that they do not exchange 

 fibres. We have, therefore, good anatomical evidence 

 that no considerable number of communis fibres enter the 

 r. hyoideus, and that independently of the fact that no 

 terminal buds are found in its course. It is equally clear 

 that no considerable number of general cutaneous fibres 

 enter the r. mandibularis VII, and this is substantiated 

 by the fact, to be noted below, that the areas in which the 

 special cutaneous fibres of the r. mandibularis VII find 

 their terminal organs receive an independent general 

 cutaneous nerve supply from the r. mandibularis V (see 

 Fig. 3)- 



^. — The Ramus Mandibularis VII. 



This nerve {inan. VII) contains lateralis and communis 

 fibres, which though bound up in the same trunk for most 

 of their courses, nevertheless correspond to the r. externus 

 and r. internus of the Amphibia and of some other fishes. 



After its separation from the r. hyoideus and imme- 

 diately upon its emergence from its canal in the hyoman- 

 dibular bone it sends a very small branch {m. VII. i) 

 around the upper edge of the preoperculum, then ven- 

 trally between this bone and the m. adductor mandibulas. 

 Here it divides, the smaller part (of coarse fibres) running 

 laterally through this muscle to the skin, close under 



