278 Human Complexion and its Causes. [May, 
of England. The inhabitants of the Mexican table-land 
are as brown as those of the tierras calientes. “ The Aymaras 
and Quichuas of the Peruvian Andes are darker than the 
Yuracaras of the forests to the eastwards. 
A further supposition is that the more carnivorous races 
of mankind are fairer than their vegetarian neighbours. In 
opposition it may be urged that the Red-skins of North 
America, who subsist almost entirely upon the produce of 
the chase, are darker than the European immigrants who 
have almost entirely displaced them. 
All these attempts at an explanation of the faCts of com- 
plexion being therefore quite unsatisfactory, there is need 
and room for a new theory. Such a one has been pro- 
pounded by Mr. J. M. Buchan, M.A., in a paper read at a 
meeting of the Canadian Institute of Toronto,* and is deci- 
dedly worthy of a careful examination. The author recog- 
nises two factors, well known to have a great influence upon 
animal and vegetable life, temperature and climate. He 
arranges climates under five heads : — 
I. Arctic. 
II. Temperate moist. 
III. Temperate dry. 
IV. Tropical moist. 
V. Tropical dry. 
Before proceeding to examine the kind of skin best 
adapted to these different climates, he gives a brief account 
of the epidermis and of its colouring-matters. Here he 
takes occasion to remark that “ the deeper the shade of the 
pigment the more rays will it reflect, and the more effective 
will it be as a protective agency. On the contrary, the 
lighter the shade the more light and heat will it permit to 
enter the body.” 
Now except the pigment of the skin possesses properties 
totally different from all those with which physicists have 
been in the habit of experimenting, this is a most perplexing 
statement. We find, by direCt trials, that the darker any 
surface the more readily it absorbs radiant heat. Water 
placed in a tin vessel coated with lamp-black will rise to a 
higher temperature on exposure to the sun than if placed in 
a similar vessel painted white. And, in virtue of the very 
same principle, water in a black can, if left in the open air 
on a frosty night, will freeze more rapidly than if it had been 
* See Popular Science Monthly, May, 1880. 
