68 MOSTLY MAMMALS 



"The part played by phagocytes," writes the author, 

 " in the whitening of the hair explains many phenomena 

 observed long ago, but not as yet sufficiently understood." 

 Thus the phenomenon of hair turning white in a single 

 night, or in a few days, may be explained by the increased 

 activity of the phagocytes, which remove the pigment 

 within an abnormally short period. 



