APPENDIX. 419 



hind feet, yet it differs in position relative to the phalangeal bones, lying on 

 the same j^lane 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 a deeper or internal layer, 

 in which the cells wei'e 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 demai'cation, 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 foi'e feet of the 

 adult Caribou. The fact of its existence in fore and hind feet of the Virginia 

 deer being well understooil, 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 i-equired 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 exjjressed 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 develojied 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 



