THE MUSCLES OF THE TONGUE. 27 



flattened fasciculus, which proceeds downwards and 

 forwards to be inserted by a delicate tendon into the 

 head of the cerato-branchial of the thyro-hyal of the 

 corresponding side on its upper aspect. When these 

 muscles contract in unison, they tend to raise the tongue 

 towards the palate, but if they act singly this member is 

 pulled to the side towards which the contracting muscle 

 is directing- it. We find that " in some birds it divides 



O 



into three or more portions : the posterior descends 

 obliquely forward, and is inserted into the tendinous 

 commissure of the mylo-hyoideus ; the middle portion is 

 inserted into the urohyal [second basibranchialj ; the 

 anterior fasciculus is inserted into the side of the 

 basihyal above the transverse hyoglossus. The actions 

 of these different portions vary according to their in- 

 sertion ; the first and second depress the apex of the 

 tongue by raising the urohyal, the third raises the tongue 

 and draws it to one side when it acts singly " (Owen). 



23. The genio-liyoideus is the largest and most 

 powerful muscle of the group we are now examining 

 (Figs. 5 and 7, and others). It arises from an extensive 

 area (two in some birds) on the inner side of the mandible 

 nearly as far forward as the horny part. The fibres 

 unite to form a broad band, transversely compressed, 

 which passes downwards and backwards until it meets 

 the outer side of the corresponding thyro-hyal, about its 

 middle ; this it envelops, by a spiral turn and a half, to 

 its very extremity. 



It is quite evident that the contraction of this pair of 

 muscles will have the effect of protruding the tongue 

 from the mouth. 



24. The cerato-liyoideus (Figs. 7 and 9). I find the 

 muscle so named by Owen to have a somewhat differ- 

 ent insertion than that eminent anatomist gives it for 



