64 
Froceedings of Royal Society of EdinhurgJi. [dec. 5, 
8. On the Colour of the Skin of Men and Animals 
in India. By Robert Wallace, Professor of Agriculture 
and Rural Economy in the University of Edinburgh. 
Indian cattle have, with few exceptions, jet hlack skins. The 
hair is frequently white, grey, hrown, or hlack, but only in rare 
cases are the skins white. The animals having white skins are 
weakly, if not unhealthy, are liable to blister with the sun, and 
contract after a time a form of leprosy. 
Black Skin an Advantage. — This opens up and widens the scope 
of a most interesting question on the relation of colour to climate, 
which — I have it on the very highest authority, that of Professor 
Huxley — is by no means at present understood. The field of 
investigation as regards India is a large one ; it embraces the human 
races, and the breeds of cattle, sheep, pigs, buffaloes, and horses. 
The skins of all, as a rule, are black or dark coloured; the few 
white exceptions I have noticed particularly in buffaloes and cattle, 
and in one case of a goat, are as stated delicate. The white or grey 
hair so prevalent in cattle extends to the Arab horse, and would 
appear to be, when associated with the black skin, peculiarly well 
adapted to resist the extreme heat of a tropical sun. It has always 
been a marvel that the white skin, which on account of its colour 
does not absorb heat so quickly as a black skin, should not prevail 
in the human species within the tropics ; and it becomes even more 
wonderful now, when it begins to dawn upon us, that the skins of 
the lower animals follow the same great law of nature, whatever 
that law may be. 
Black Skin Theory Explained. — It would seem at first sight that 
the black skin should rather be a disadvantage than otherwise ; but 
in the reality it is not so. The black colour of the skin causes it to 
absorb more heat than a white skin, but while it is doing so, at the 
same time and for the same reason, it is giving off more heat — 
its absorbing power and also its radiating power being greater. 
Therefore, when the sun’s rays impinge upon the skin, the heat is 
rapidly absorbed; but, as the rate of absorption of heat is greater 
than the rate of radiation, unless the temperature of the skin were 
lowered by some other influence, the whole surface of the body 
would become extremely hot. 
