APPENDIX. 419 
hind feet, yet it differs in position relative to the phalangeal bones, lying on 
the same plane as that of the anterior wall of the web, its own anterior wall 
being incorporated with the under surface of the skin and thereby shortened 
to about one quarter of an inch in length; the posterior wall, however, remains 
distinct and measures from the blind extremity to its termination somewhat 
over an inch. 
The microscopic examination of this organ proved it to be of epidermic 
origin. Sections through the thickness of its walls showed an external layer 
of flattened prismoidal cells with small nuclei, and « deeper or internal layer, 
in which the cells were more rounded and filled with protoplasm. This differ- 
ence in the uppermost and lowermost layer was brought out by the staining 
process, and it is in these only that we find the line of demarcation, the inter- 
vening layers merging gradually one into the other. Other structures observed 
were the hairs and hair follicles with their accompanying tissues and some 
fibres, representing no doubt the true skin, which is not developed in these 
organs to any considerable extent. 
The two layers of cells correspond to the same parts in man, namely, a 
horny layer external, but of course internal in the cul-de-sac, a mucous layer 
external when the sac is dissected from its surroundings, the changed position 
of these layers is owing to the circumstance of the sac’s being an invagination 
of the epidermic layer into the true skin. 
Regarding the functions of this structure various and contradictory opinions 
are expressed, that of its being glandular being most prevalent ; again it is 
said to have no existence in the wapiti and moose and in the fore feet of the 
adult Caribou. The fact of its existence in fore and hind feet of the Virginia 
deer being well understood, its presence in the animal is said to be for the 
purpose of leaving a trace or scent on the ground, and in this way serving the 
union of the sexes at certain seasons; but if this is the case, we may ask why 
should it not exist in the wapiti, and be fully developed in the Caribou and 
moose, since it must be obvious to us that the fulfillment of the conditions 
which obtain in the Virginia deer, are required also in the wapiti. More than 
this, we know that a true scent organ in the Caribou is situated on the inside 
of the heels or gambrils. 
On the occasion of my first dissection of this structure in the Caribou buck 
fawn, I expressed the opinion that it would be found also in the fore feet of 
the adult animal, though perhaps more rudimentary, and a subsequent exami- 
nation of an adult doe has fully confirmed this opinion, since I found this 
structure as well developed as in the young animal. I now feel more than 
ever convinced that it exists in all our deer tribe, not excluding the wapiti, 
although it may be larger in some than in others; an immature living moose, 
in possession of Mr. J. W. Stairs, being provided with it. 
The following summary of its histological relations will aid in arriving at 
correct conclusions relative to its importance : — 
1st. It is a growth or offset from the epidermic layer of the skin invagi- 
nated between the phalangeal bones, containing the malpighian and horny 
layers of the epidermis, and carrying with it a very thin layer of the true 
skin. 
2d. Hair follicles, and hairs grow from its internal walls, and emerge 
through its opening, these being also epidermic, or of epithelial origin. 
3d. The absence of glandular tissue, excepting the sebaceous follicles which 
