128 STRONG. [Vol. X. 



M. mylohyoideiis posterior (== submaxillaris post. = intermaxil- 

 laris post. = subhyoideus) and the other supplying the skin 

 below this muscle. There is, thus, quite a marked resem- 

 blance to the branch of the R. mandibularis V which innervates 

 the M. mylohyoideus anterior and the skin below it. The 

 R. hyoideus, however, is composed of fibres from two nerves, 

 the VII and the IX. 



While it is difficult to distinguish the two sets of fibres in 

 the R. hyoideus VII, yet it is probable, from direct observation 

 alone, that the fibres from VII ab are those which innervate 

 the muscle. 



It is obvious from the preceding that the cutaneous part of 

 the R. hyoideus does not belong to the lateral line system of 

 nerves to the head, and belonging to the VII. As this cutane- 

 ous component is derived from the IX-j-X, it will be further 

 treated below. 



The remainder of the R. hyomandibularis proceeds cephalad, 

 and soon divides again (368). Of these two divisions the ven- 

 tral one comprises the remainder of the communicating branch 

 from the IX-|- X and ^ Yllb, while the dorsal one comprises 

 the remainder of VII ab and all of VII aa (fasciculus communis). 

 The former is the R. mandibularis externus. It proceeds ven- 

 trad just inside the M. orbitohyoideus. The bulk of the coarse 

 fibres belonging to ^ VII /^ have become aggregated on its 

 outer side. As the nerve emerges on the ventral side of the 

 muscle it becomes divided into two branches, an inner and 

 lower (mand. ex. a)jy composed of the finer fibres of the IX-j- X 

 component, together with a few coarse fibres, and an outer 

 branch (mand. ex. b) comprising the coarse fibres of >^ VII by 

 together with a portion also of the finer fibres of the commu- 

 nicating branch from the IX -f X. 



The former of these two branches (mand. ex. a) sends off a 

 small twig, which is reenforced by fibres from the other branch, 

 and supplies the skin. The remainder, in every way resembling 

 the cutaneous portion of the R. hyoideus, proceeds caudad and 

 ventrad, and is distributed to the skin of the ventro-lateral 

 aspect of the body in this region. No connection was observed 

 between it and lateral sense organs. It is a ^^ general cutaneous " 



