CONTRIBUTIONS TO ZOOLOGICAL ANATOMY. 
By JAMES Mercer, M. D., Fellow of the Royal College of Sur- 
geons , and Lecturer on Anatomy , fyc. Edinburgh. 
[Continued from page 412.] 
VIII. — On the Structure and Uses of the Tongue , considered as 
an Organ of Taste and of Prehension in Graminivorous and 
Herbivorous Animals. 
It is the generally received opinion that the principal uses of the 
senses, by virtue of the peculiar properties of their nerves, are to 
make us acquainted not only with the states of our own body, but 
also to inform us of the qualities and changes of external nature, in 
as far as these give rise to changes in the condition of these nerves. 
This change, termed sensation, is a property common to all the 
senses; but the kind of sensation being different in each, — in that 
of light, of sound, of smell, of taste, and of touch. 
When we come, therefore, to review these different senses, and 
observe the manifold conveniences which they individually confer 
on the animal exhibiting them, the distribution which has been 
made of them by physiologists, into those possessing “ special pro- 
perties,” and those possessing “ properties more or less similar to 
each other,” appears to be one founded on facts which can be 
easily demonstrated, and on conclusions which must be deduced 
from the facts so produced. 
But if we take up a wider range of inquiry, and extend our re- 
searches into the fertile field of Comparative Anatomy, we shall 
find abundant evidence there, that some of those organs, which in 
man and in the higher classes of animals perform only the part 
of a special sense, in others contribute very materially to the per- 
formance of general functions, such as the ingestion of food, and 
the affording of assistance to and defending the animal against the 
attacks of others. The first of these divisions, the “ organs of 
special sense,” comprise the organs of vision and of hearing ; 
whilst the second embraces the remaining three, the organs of 
smell, of taste, and of touch ; but, on analyzing these latter more 
minutely, it would not be difficult to shew, that their arrangement, 
physically considered, is not strictly correct. 
The organ of vision, for example, requires for its peculiar 
stimulus to exertion the existence of luminous rays transmitted to, 
and impinging on, its special nerve; and the organ of hearing, in 
