THE MUSCLES 6i 



complete, and larger, than that formed at the origin of the M. sub- 

 hyoideus. The fibres run more or less parallel with the cartilage on 

 its ventral side, and are inserted on the ventro-anterior border of the 

 expanded anterior end of the cerato-hyal. It thus forms a muscular 

 link connecting the opposite ends of the two cartilages. 



Innervation: By several fine twigs from the N. glossopharyngeus 

 (IXth) which passes along its dorso-mesial border, and also from 

 a nerve formed by the fusion of twigs from the recurrent branches 

 of the nerves of the visceral arches (Xth). 



Function : The obvious result of the contraction of this muscle is 

 to advance the branchial arches, and their associated copula, relative 

 to the cerato-hyal, and, since the movement of this latter element in 

 a posterior direction is limited by the lig. hyoquadratum, the muscle 

 is able to have a positive effect on the branchial apparatus relative 

 to the jaws as well. It also serves to transmit to the branchial arches 

 the movement occasioned by the M. subhyoideus. 



Driiner (1901, p. 526) gives an admirable account of the action 

 of these two muscles in extruding the tongue to secure food, based 

 on experiments carried out by him on pithed animals, consisting of 

 applying an electrical stimulus to the nerves concerned, and also on 

 observations made on the living animal. The substance of his account 

 is given below. 



As already explained, the action of the M. subhyoideus is to ad- 

 vance the cerato-hyal, first in an antero-dorsal direction, and later 

 to tip the anterior end of the cartilage more dorsalwards. Now if the 

 jaw is simultaneously opened wide, as it is in snapping at prey, the 

 effect is to cause the dorsal surface of the tongue to face directly 

 forwards, the action of the M. subhyoideus alone being about suffi- 

 cient to bring the surface of the tongue to the level of the snout. The 

 cerato-hyal being held in this position by the M. subhyoideus, its 

 anterior end becomes Tipunctumfixum for the M. subarcualis rectus i, 

 which, by its rapid contraction, forces the branchial arches and the 

 copula, together with the tongue, still farther forwards. The muscle 

 also pulls the posterior end of the cerato-branchial i ventralwards, 

 causing the arches to twist about the copula and thus to force it still 

 farther forwards. The combined result of these operations is to 

 project the tongue to a surprising distance in front of the mouth so 

 as to secure the prey on its sticky dorsal surface. The tongue, with 

 its adhering food, is returned to the mouth by the action of muscles 

 subsequently to be described — MM. hyoglossus and rectus cervicis. 

 When the mouth has been shut the MM. subhyoideus and sub- 

 arcualis rectus I again come into play so as to force the tongue 



