326 HUMAN BIOLOGY 



environment to induce any important change, unless the 

 pigmentation is so unfavorable that the race tends to die out. 

 If mutations occur on a large scale, a rapid change is of 

 course possible, but barring that a moderately fair race, if it 

 lives out of doors and becomes well tanned, can presumably 

 subsist in a tropical region for thousands of years, provided it 

 is adapted to the environment in other ways and is not in 

 competition with a darker race. 



Other forms of adaptation can be scarcely more than 

 mentioned. One is the condition of the sweat glands of the 

 skin. Among Negroes and other dark races the sweat 

 glands are more numerous, smaller, and less active than 

 among white people. They flood the skin with fine droplets of 

 moisture, but do not pour out such streams of perspiration as 

 do the glands of the white man. Another apparent adaptation 

 is found in the form of the nose. Among northern races the 

 nostrils tend to be small and relatively round, not admitting 

 a large amount of air at one time, and forcing the air to pass 

 through a relatively long passage where it is warmed before 

 reaching the throat. Among Negroes on the other hand, the 

 nostrils are short, and wide open so that large amounts of air 

 can be taken in at once. Such a condition is favorable in a 

 warm climate where the heat often compels rapid breathing 

 even when people are at rest. But is decidely disadvantageous 

 where the temperature ranges far below zero, and may be an 

 important reason why colored people do no thrive in regions 

 like the most northerly parts of the United States. 



The relation of mental characteristics to climate is not so 

 obvious as that of physical characteristics. Most biologists 

 believe that there are mental as well as physical differences 

 among races; many say that the brain, being the most 

 recently evolved organ, is likewise the most variable. Yet an 

 important group of anthropologists and psychologists deny 

 this ; all mental differences which others call racial, so they say, 

 are due to training and social inheritance. Although the 

 brain varies in size and intricacy from race to race and in that 

 respect is like the skin, sweat glands, nose and other organs, 

 it is assumed to be uniform in its functions. A more reasonable 

 view seems to be that the powers, aptitudes and functioning 

 of the brain vary like those of any other organ and are 



