Joe ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
identical in all of these mammals. Let us examine the consequences 
of this special condition, consisting, I may repeat, in the absence of 
cutaneous glands. The physiological function of these glands is very 
important.?° It is superfluous to recall that the sebaceous impreg- 
nation gives the fur in general its isolating properties and imparts 
to each of its elements, the hairs, an impermeability, thanks to which 
they resist with a well-known strength all disintegrating agents, and 
notably those which are atmospheric. Everyone knows to what de- 
eree the presence of the grease produced by the sebaceous glands 
renders wool resistant and isolating, and to what degree the total 
lack of this fatty matter lessens the quality of woolen goods. Com- 
parative anatomy gives, moreover, some instructive information as 
to the part played by this impregnation. Mammals deprived of 
sebaceous glands are very rare; the two-toed sloths (Choloepus) 
of Central and South America and the golden moles of Africa 
(Chrysochloris) are in this condition; but it is well known that the 
sloths are particularly sensitive, even in their own country, to cold 
and damp. 
The very peculiar fur of the mammoth thus furnished only a pre- 
carious protection against cold, a protection analogous to that enjoyed 
at present by a few mammals of the tropical zone. its dermis was, 
it is true, very thick, but no more so than that of the existing ele- 
phants. It appears to me impossible to find, in the anatomical exam- 
ination of the skin and pelage, any argument in favor of adaptation 
to cold. It has been thought that the reduction of the ears, thick 
and very small relatively to those of the elephants, was the result of 
such an adaptations and indeed this character might be so under- 
stood in this sense; such large and thin ears as those of our elephants 
would probably be very sensitive to the action of cold. But it has 
also been suggested that the fattiness and the peculiar form of the 
tail in the mammoth was an adaptive character of the same kind; 
however, it is to the fat-rumped sheep, animals of the hot regions, 
whose range extends to the center of Africa, that we must go for an 
analogue to this last character. 
Ji is, therefore, only thanks to entirely superficial comparisons 
which do not withstand a somewhat detailed analysis, that it has been 
possible to regard the mammoth as adapted to the cold. On account of 
10Tt is merely necessary to mention that according to the opinion now accepted, that of 
Unna, the effect of the sebum is to lubricate the fur, thus protecting it against disintegra- 
tion, and that of the sweat is to soak the epidermis with an oily liquid, protecting it also 
against desiccation and disintegration. In reality the deposit of sebum on the surface of 
the skin, so easy to observe in the human species, especially in certain cases of baldness in 
which it becomes excessive, contributes also to the protection of the integument. In the 
absence of sebum and sweat the only fatty impregnation of the epidermis is that which 
comes from the action of the cells of the epidermis itself; this action remains, in any 
event, very special and very limited, and the absence of the glandular secretions puts the 
skin in a condition of less resistance well known in dermatology. 
