'^ HOW ARCTIC ANIMALS TURN WHITE 



Although I have not the details of any one particular case 

 before me, so many instances are chronicled in which the 

 hair of human beings, under the influence of strong mental 

 emotion due to terror or grief, has become suddenly 

 blanched within a single night or some such period of 

 time, that the occasional occurrence of such a phenomenon 

 must apparently be accepted as a fact. Such a change is, 

 of course, due to the bleaching of the pigment with which 

 the hair is coloured, although we need not stop to inquire 

 by what particular means this bleaching is accomplished ; 

 all that concerns us on the present occasion being to know 

 that the hair in man may turn white in this manner under 

 abnormal circumstances. And there appears to be evidence 

 that under equally abnormal conditions a similar change 

 may take place suddenly in the hair of the lower animals. 

 This is exemplified by the well-known experiment made 

 considerably more than half a century ago by Sir John 

 Richardson on an Arctic lemming — a small mouse-like 

 rodent, which habitually turns white in winter, although 

 dark-coloured in summer. In this instance the little 

 animal was kept in a comparatively warm room till winter 

 was well advanced, when it was suddenly exposed to a 

 temperature of 30° below zero ; a continued exposure to 

 this and a still more intense degree of cold eventually 

 resulted in its death, which took place within three 



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