TONGUE OF THE ANT-EATEK. 789 



each other by rubbing their grinding surfaces in all needful directions. 

 In the Herbivorous quadrupeds these triturating motions are likewise 

 extensive. In the EODENTIA the movements of the lower jaw are prin- 

 cipally backwards and forwards, thus giving free play to their chisel-like 

 teeth whilst employed in eroding hard substances ; and in the CARNIVORA, 

 where there is no necessity for any grinding motion, the condyle is so 

 locked into a deep and transverse glenoid cavity, that the movements of 

 a hinge only are permitted. 



(2281.) But whatever the degree of motion conferred upon the lower 

 jaw, the muscles that act upon it are exactly comparable to those of the 

 human subject. The masseter is strengthened in proportion to the hard- 

 ness of the substances used for food ; the temporal covers a greater or 

 less extent of the cranium as the jaws are stronger or more feeble ; and 

 even the pterygoid muscles differ only in relative size and form from 

 those of Man. 



(2282.) The digastric muscle, however, which is an important agent 

 in depressing the lower maxilla, does not preserve the same arrange- 

 ment in the lower quadrupeds that it presents in the human species. 

 In Monkeys, indeed, it still exhibits two fleshy bellies, and a central 

 tendon that traverses the stylo -hyoideus ; but in general it is a single 

 fleshy muscle, arising from the neighbourhood of the mastoid process, and 

 inserted near the angle of the jaw. 



(2283.) The tongue, in nearly all the Mammifera, is composed of the 

 same muscles as in Man ; and their disposition is so similar as to render 

 any detailed enumeration of them quite unnecessary. The only excep- 

 tions worthy of notice are found in the Ant-eater (MyrmecopTiaga) 

 and in the Echidna, animals possessing tongues of remarkable length 

 and slenderness, by means of which they secure their insect prey. 



(2284.) In both these animals the tongue suddenly becomes much 

 contracted at the place where it begins to be free from the surrounding 

 parts. It then appears to be made up of two very long and slender 

 muscular cones, laid one upon the back of the other, their apices being 

 at the end of the tongue *. Each of these cones consists of two muscles : 

 one external, composed of a multitude of distinct fasciculi investing the 

 internal muscle in a circular manner, and forming around it numerous 

 little rings resembling the annelli of an earthworm. The internal 

 muscle, on the contrary, is of great length ; it arises from the middle 

 and upper part of the sternum, runs forward along the neck, passes 

 between two layers of the mylo-glossus, and afterwards becomes sur- 

 rounded by the annular muscle ; it is composed of distinct fasciculi, 

 rolled upon themselves in an elongated spiral ; the external fibres termi- 

 nate at the first rings ; those beneath attain the rings that succeed, and 

 so on until the innermost fibres reach quite to the extremity of the 

 tongue. It is easy to perceive that, by its action, this muscle will 

 * Cuvier, Le9ons d'Anat. Comp. iii. p. 264. 



