THE MUSCLES 65 



the only one of the MM. laryngei of the larva which persists to the 

 adult stage. The M. laryngeus ventralis may, however, be repre- 

 sented by a few fibres passing from the lateral end of the lig. dorso- 

 laryngeum to the ventral inscription of the M. constrictor laryngis 

 (Driiner, 1901, p. 532). 



Innervation: From the R. recurrens n. intestinalis X. 



Function: It constricts the larynx, closes the glottis, and is the 

 antagonist of the M. dilatator laryngis. 



6. Muscles of the Head supplied by Spinal Nerves (PI. VI, figs. 

 37 and 38). 



M. genio-hyoideus (m.g.hy.), Carus (1828); Fischer (1843); Mivart 

 (1869); Osawa (1902). 



Rectus lingualis ....... Funk (1827}. 



Levator maxillae inferioris s. Geniothyroideus . v. Siebold (1828). 



Genio-sous-hyoidien ...... Duges (1834). 



Genio-hyoidien .... Cuvier (1835); Rusconi (1854). 



Genio-hyoidei-mandibularis .... Stannius (1854-6). 



Levator maxillae inferioris longus Schmidt, Goddard, and van d, 



Hoeven (1864). 



Genio-branchial ...... Humphry (1872). 



Maxillo-hyoideus (genio-hyoideus) . . Hoffmann (1873-8). 



Genio-hyoideus s. rectus superficialis hypobranchialis anterior 



Driiner (1901). 



After removing the skin from the floor of the mouth and throat, and 

 turning back the MM. intermandibularis and interhyoideus a pair 

 of strong longitudinal muscles are exposed — they are the MM. 

 genio-hyoidei. They may be regarded as arising from the inner edge 

 of the lower jaw immediately lateral to the origin of the M. genio- 

 glossus, and then, passing backwards and mesialwards, the fibres 

 from either side become very closely approximated in the middle 

 line as they continue their course backwards. The right and left 

 halves of the muscle may remain distinct, but there is often some 

 crossing over and mingling of the fibres. In the larva the muscle is 

 inserted on the posterior end of the uro-branchial cartilage, and in 

 the adult the bulk of the muscle remains attached to the vestige of 

 this cartilage, the os triangulares but some fibres spread to a tendinous 

 inscription which extends in a transverse plane from the lateral 

 extremities of this bone. In addition a small bunch of the most 

 lateral fibres are inserted on the capsule of the thyroid gland. There 

 is, however, some considerable variation in the exact relations of the 

 muscle at its insertion. 



4038 F 



