THE WHITE WINTER COAT 341 



In a famous experiment made by Sir John Ross, a 

 Hudson's Bay lemming was kept in the cabin of the 

 ship through the winter and did not change colour. But 

 on the first of February it was exposed on deck and it had 

 several white patches next day. It turned white in a week, 

 and died a few days afterwards. In this case the blanching 

 must have been due to a change in individual hairs, such 

 as sometimes occurs very rapidly in man as the result of a 

 nervous shock. It is probable, as Mr. F. E. Beddard points 

 out in his interesting book on Animal Coloration (1892), 

 that the suddenness of the change robbed the experiment 

 of part of its value in proving that the cold is the stimulus 

 that induces the blanching. " The cold was administered 

 in a sudden dose, which may have produced an effect 

 analogous to a nervous shock." 



In the case of the American hare, the investigations 

 of Welch (Proc. Zool. Soc., 1869) seem to show that the 

 process of assuming the white colour is twofold. On the 

 one hand, there is a new growth of white hair ; on the 

 other hand, there is a slow blanching of coloured hairs. 



The whiteness of hair or feathers is due negatively to 

 the absence of the usual pigment, and positively to the 

 presence of minute gas bubbles in the cells. A new white 

 hair or feather is not in any special way difficult to under- 

 stand, it simply implies some slight change in the chemical 

 processes involved in all development. The pigment is 

 not formed or not completely formed, and gas vacuoles 

 are abundant in the cells. It seems, sometimes, as if the raw 

 material (or chromogen) of the pigment were present, but 

 the magic touch of the ferment required to make this a 

 coloured stuff is absent. 



When a hair already coloured becomes white very 

 suddenly, there seems to be a rapid change in the pigment 

 material, which ceases to be coloured. It is well known 



