COMPARATIVE ANATOMY. 
ORGANS OF SENSE. 
Few subjects in comparative anatomy 
and physiology have given rise to more va- 
rious and contradictory opinions than the 
organs of sense in some classes of animals. 
Much misunderstanding on this point has 
clearly arisen from the inconsiderate and 
unconditional application of inferences 
drawn from the human subject to animals. 
Thus it has been supposed, that those which 
possess a tongue must have it for the pur- 
pose of tasting, and that the sense of smell 
must be wanting where we are unable to 
ascertain the existence of a nose. Observa- 
tion and leflection will soon convince us, 
that the tongue, in many cases (in the ant- 
eaters among the mammalia, and almost 
universally in birds), cannot from its sub- 
stance and mechanism be considered as an 
organ of taste ; but must be merely subser- 
vient to the ingestion and deglutition of the 
food. Again, in several animals, particularly 
among insects, an acute sense of smell seems 
to exist, although no part can be pointed 
out in the head which analogy would justify 
us in describing as a nose. 
However universally animals may possess 
that feeling which makes them sensible to 
the impressions of warmth and cold, very 
few possess, like the human subject, organs 
exclusively appropriated to the sense of 
touch, and expressly constructed for the 
purpose of feeling, examining, and exploring 
the qualities of external objects. 
This sense appears, according to our pre- 
sent state of knowledge, to exist only in 
three classes of the animal kingdom ; viz. in 
most of the mammalia, in a few birds, and 
probably in insects. 
The structure of the organ of touch is the 
most perfect, and similar to that of the hu- 
man subject in the quadrumana. The ends 
of their lingers, particidarly of the posterior- 
extremities, are covered with as soft, and 
delicately organized a skin as that which 
belongs to the corresponding parts in man. 
Several of the digitata are probably pro- 
vided with this sense. The organization of 
the under surface of the front toes of tire 
racoon (ursus lotor), and the use which the 
animal makes of those parts, prove this as- 
sertion. 
It is not so clear that we are authorised 
in considering the snout of the mole and 
pig, not to mention the tongue of the soli- 
dungula and bisulca, or the snout of these 
and other animals, as true organs of louch 
according to the explanation above laid 
down. 
Much less can we suppose tlie long bristly 
hairs, which constitute the whiskers of the 
cat-kind, and other mammaiia, to be organs 
of touch in tlie sense we are now consider- 
ing, although they may be serviceable, when 
they come in contact witli any object, in 
warning, and making the animal attentive. 
Bats have been supposed to possess a pecu- 
liar power of perceiving external objects, 
without coming actually into contact with 
them. In their rapid and irregular flight 
amidst various surrounding bodies, they ne- 
ver fly against them ; yet it does not seem 
that the senses of hearing, seeing, or smelling, 
serve them on tliese occasions; for they 
avoid any obstacles with equal certainty 
when the ear, eye, and nose are closed. 
Hence natiualists have ascribed a sixth 
sense to these animals. It is probably ana- 
logous to that of touch. The nerves of the 
wing aie large and numerous, and distribut- 
ed in a minute plexus between the integu- 
ments. The impulse of the air against this 
part may possibly be so modified by the ob- 
jects near which the animal passes, as to in- 
dicate their situation and nature. 
In geese and ducks the bill is covered 
with a very sensible skin, supplied with an 
abundance of nerves from all the three 
branches of the fifth pair. This apparatus 
enables them to feel about for their food in 
mud, where they can neither see nor smell 
it. None of the amphibia or fishes seem to 
possess the sense of touch, according to the 
acceptation stated above. 
All the observations and investigations of 
the structure of the antennae, those peculiar 
organs which exist universally in the more 
perfect insects, and of the use which these 
animals generally apply them to, lead us in- 
evitably to the conclusion that they really 
are proper organs of touch, by which the 
animal examines and explores surrounding 
objects. Such organs are particularly ne- 
cessary to insects, on account of the insensi- 
bility of their external coat, which is gene- 
rally of a horny consistence, and also from 
their eyes being destitute in most instances 
of the power of motion. 
TONGUE. 
Most of the herbivorous mammalia, par- 
ticulariy among the bisulca, have their 
tongue covered with a firm and tiuck cuti- 
cular coat, which forms numberless pointed 
papillse directed backwards. These must 
assist, according to their consistence and 
direction, at least in the animals of this 
country, in tearing up the gras.s. Animals 
