THE MUSCLES OF THE TONGUE. 29 



the class, generally. Of it, lie says that " it passes from 

 the thyrohyal to the urohyal, and is therefore sub- 

 servient to the lateral movements of the tongue " (Anat. 

 Verts., vol. ii. p. 154). This duty it also performs in 

 the Kaven, where we find it arising on the under side of 

 the shaft of the epibranchial element of the thyro-hyal 

 by a delicate tendinous slip. This soon becomes muscular 

 as it passes forwards, forming a long slender belly, which 

 is closely applied to the hyoid. Opposite the first 

 basibranchial it is again a long tendinous slip, and thus 

 remains until it is finally inserted into a little bony 

 elevation on the under side of the anterior end of the 

 corresponding cerato-hyal. 



Owing to the free lateral movements enjoyed by the 

 joint at the anterior end of the first basibranchial, it is 

 quite clear that either of these muscles acting singly 

 must pull the tongue to one side. But the joint referred 

 to also operates in the opposite direction, so that, united 

 action of the pair would tend to depress the tongue. 



25. The sterno-hyoideus (Figs. 9 and l7). — Agreeing 

 with the majority of birds, we find in the Eaven either 

 sterno-hyoideus arising from the anterior surface of the 

 thyroid bone of the superior larynx. The muscular fibres 

 at the origin are quite fleshy, but as they converge and 

 pass forwards, they become rather more tendinous, and 

 are thus constituted as they are inserted into either 

 cerato-hyal at its base. Other fibres, which hold a more 

 mesial position, unite with the corresponding ones of the 

 muscle of the opposite side, to pass into and finally be 

 lost in the tissue composing the soft part of the tongue, 

 at its base. These latter are not well shown in Fig. 17, 

 as they are huddled together by the traction of the little 

 dissecting hook and chain, which pulls the muscle to one 

 side so that the depressor glossus may be seen. 



