THE GLANDS. 249 
wanting. In this regard he is precisely like our moose, so we 
must dispense with his fourth section. 
‘We may briefly summarize these sections thus: First, where 
the outside tuft is present and the inside wanting, Second, where 
both are present, and Third, where the inside tuft is present and 
that on the outside wanting. This certainly divides the genus 
into very natural sections easily recognized. 
By a careful study of these tufts of hair and the structures 
which they indicate and cover, I find we are enabled with equal 
certainty to subdivide these sections and designate the species 
composing them respectively. Dissection, with aid of the micro- 
scope, shows us that each of these tufts of hair indicates the place 
of, and covers and surrounds a cutaneous gland, a distinct organ 
which in the economy of the animal has its proper and peculiar 
functions to perform. When we find such an organ present in 
one class of animals, and absent in another class sufficiently re- 
sembling them to be ranked in the same genus, we are almost 
prepared to declare them to be specifically different, and are led 
at once to look for other difference to corroborate the suspicion. 
A distinct member, always constant in all its features, among all 
the individuals of a class who freely associate together, wherever 
such association is permitted without restraint, and who avoid 
the society of all other similar animals destitute of that member, 
—this peculiarity adds to the suspicion of a specific difference ; 
and so on, whenever we can find differences either in structure 
or habit which cannot be assigned to accidental or factitious cir- 
cumstances or surroundings, such as climate, altitude, aliment, 
and the like, we are more and more inclined to draw the dividing 
line of species. But whenever we can ascribe peculiarities either 
of structure or habit to such accidental surroundings, we may 
conclude that the differences would gradually disappear on a 
change of circumstances ; then we may be justified in the opinion 
that the change is transient and we have but a variety. 
I know of no feature or member of any of these animals so 
exactly alike, in dimensions, location, coloring, and structure, on 
every individual of each species of our deer, as these tufts of 
hair and the glands which they conceal, and yet those on the 
outside of the metatarsus are entirely different from each other 
on the different species, and this difference is so great that when 
one’s attention is once called to them the most casual observation 
is sufficient to identify them, and enable us to say, with certainty, 
to which species they belong. We look in vain for any other 
