CONTRIBUTIONS TO ZOOLOGICAL ANATOMY. 
589 
In figure and external conformation, the tongue presents a con- 
siderable difference in the herbivorous from the canine and feline 
classes of animals. In the former, though formed of two symme- 
trical portions, as in all animals, yet it distinctly consists of a 
narrow, elongated, and extremely moveable portion, the tip, serving 
the purpose of prehension ; and of a thick, firm, and comparatively 
immoveable portion, the body, attached to the hyoid bone, and evi- 
dently serving the purpose of gustation. 
In the latter classes, this antero-posterior division is not so pro- 
minently developed ; but instead thereof, it is formed of two dis- 
tinctly symmetrical portions, joined to each other along the mesial 
line, and which latter presents the appearance of a smooth hollow 
channel, the linea albescens, or worm of the tongue. This linea 
albescens can be seen to exist in the tip of the tongue of the her- 
bivorse, but there is no trace of it on the body. In both these classes 
of animals there is also a considerable difference in the situation, 
form, and arrangement of the chondro-mucous papillse or appendages 
that are developed from the membrane investing the entire dorsum 
of the organ, and which will be specially considered when treating 
of this structure. 
As the function of the tongue, therefore, evidently consists of 
two kinds, I shall consider its structure under two heads, the mus- 
cular or basement structure, for motion (including insalivation and 
the primary part of deglutition) ; and, secondly, the investing mem- 
brane, with its appendages, the papillae, as contributing to that of 
prehension and taste. 
Under the head of the muscles of the tongue there are three 
groups to be included : first, the extrinsic muscles of the tongue; 
secondly, the intrinsic muscles of the os hyoides; and, thirdly, the 
intrinsic muscles of the tongue. 
First Group . — The Extrinsic Muscles of the Tongue. 
( The Elevators of the Os Hyoides.) 
Under this group of muscles are included those that, by their 
single or combined movements, tend to carry the os hyoides up- 
wards and forwards, under cover of the branches of the lower jaw. 
It embraces four pairs, viz. the 
Digastricus. 
Stylo-hyoideus. 
Mylo-hyoideus 
Genio-hyoideus. 
Dissection . — This group of muscles are easily shewn by placing 
the head upon its side, and in a concave block, and keeping the 
muzzle well bent backwards over the poll. The integument and 
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