1150 



TONGUE. 



movement, and, in an instant, the tongue has 

 been shot out, has again disappeared, and 

 with it its prey has disappeared too, the 

 whole being performed with a velocity that 

 startles one afresh every time it is witnessed. 

 Aves. The tongue of birds may be stated, in 

 general, to be, like that of reptiles, prehensile 

 and non-gustatory. Taste and mastication, 

 or, at any rate, taste and some delay of the 

 food in the mouth, always go together; in 

 birds the food experiences no delay in the 

 mouth, but, in almost all cases, is bolted at 

 once. In most instances, true prehension, or 

 the seizing of the food, is performed by the 

 bill, in soine few by the tongue ; in nearly all, 

 however, the securing of it when in the mouth 

 is effected b> the tongue, which is armed near 

 the base with numerous spines, directed back- 

 wards (fig. 763. ABD), that prevent the 

 regress of the prey, whether alive or dead, and 

 which, with a similar structure at the roof of 

 mouth and throat, must greatly assist the first 

 stage of deglutition. The structure of the 

 tongue of birds is generally such as not to 

 acimit of intrinsic elongation ; its protrusion 

 therefore can only be effected by the move- 

 ment of the organ en masse ; and this is pro- 

 duced to a surprising extent by a particular 

 arrangement of the hyoid bone and its muscles, 

 which I will now describe. The general cha- 

 racter of the hyoid bone of birds, as already 

 stated, is elongation longitudinal extension, 

 and to this add the fact of the suppression, 

 entire or partial, of osseous or ligamentous 

 attachment of the hyoid elements to the skull, 

 such attachment being inconsistent with the 

 required free movements of the organ. From 

 the posterior part of the body of the hyoid 

 bone project back the slender posterior cor- 

 nua forming, by their divergence, an acute 

 angle, embracing in its apex the upper part of 

 the larynx : as they pass beneath the occiput 

 they curve upwards, and are surmounted by 

 slender pieces, frequently cartilaginous (cerato- 

 branchial), having a still greater curvature; so 

 that the whole greater cornua, as thus consti- 

 tuted, embrace the back of the skull, to the 

 shape of which their curve is moulded, and on 

 which they are made to glide backwards and 

 forwards by the muscles that regulate the 

 protrusion and retraction of the tongue. The 

 principal of these muscles are two pair ; the 

 first the analogue of the stylo hyoid, which 

 retracts the tongue, and the second pair 

 which Cuvier has called the analogue of the 

 genio hyoid the conical muscle of Vicq 

 d'Azyr, which draws the tongue forwards : 

 the obliquity and length of these muscles, 

 and the free unattached suspension of the 

 hyoid apparatus, render the movements of 

 the tongue very free, and their range exten- 

 sive. The retrahent muscle, the stylo-hyoid 

 (fig. 762. a.), arises from the posterior part of 

 the lower jaw, and passes forward to be in- 

 serted into the upper surface of the junction 

 of the cornua and body of the hyoid : in 

 some birds it is more voluminous than in the 

 species figured, and has a more extended 

 insertion ; it retracts the tongue. The pro- 

 trusor ( &.), which Cuvier has named, with 



apparently insufficient reason, the analogue 

 of the genio hyoid, arises from the inner 



Fig. 762. 



Muscles of the Tongue of the FieIdfare(T\irAus pilaris). 

 a, retractor; b, protrusor; c, cerato-glossal. 



side of the lower mandible, passes downwards 

 and a little backwards to the posterior cor- 

 nua, which it embraces in its fibres from the 

 point where it comes in contact with it to 

 its extremity : the fibres become increasingly 

 oblique as they pass back, and embrace the 

 cornua in a muscular cone, which, by its con- 

 traction, causes the cornua to slide forwards in 

 it, and so protrude the tongue . in the wood- 

 pecker, in which the hyoid cornua pass com- 

 pletely round -the head and into the upper 

 mandible, this muscle is of proportionate 

 length. Besides these, there is a mylo hyoid, a 

 thin layer passing from the lower mandible to 

 a median fibrous line, and a cerato-hyoid pass- 

 ing from the posterior cornua to the uro-hyal, 

 approximating these, and so directing the apex 

 of the tongue to the opposite side. Fig. 7 62. c. 

 is a small muscle, which I cannot find de- 

 scribed ; it passes from the under surface of 

 the basi- or glosso-hyal to the greater cornua, 

 into which it is inserted within the sheath of 

 the conical muscle. I would suggest the name 

 of cerato glossal for it ; its action is to in- 

 crease the curvature of the cornua, and there- 

 by draw the tongue back. 



Fig. 763. represents some different forms of 



Fig. 7G3. 



