374 THE BIOLOGY OF THE SEASONS 



pigment or only a few. " It is thus indubitable," Metchnikoff 

 says, " that the phagocytes of the hairs swallow up the 

 granular pigment of the cortical layer and transfer it 

 elsewhere, the result being the complete whitening of such 

 hair." This interesting discovery brings the whitening of 

 the hair into line with other processes in which phagocytes 

 play an important part. If it should be insisted that 

 even here there is senile atrophy, we are quite willing to 

 yield the point the contrast would remain, however it 

 is phrased, between relatively trivial and superficial changes 

 in old age and others which imply the thoroughgoing 

 degeneration of important structures. 



Something more serious than an absorption of decora- 

 tive pigment was revealed in MetchnikofFs study of an 

 aged parrot. It is known that these big-brained birds 

 often live to a great age ; for, although we may not accept 

 Humboldt's famous story of an aged parrot that spoke the 

 at uric language of a tribe of American- Indians for years 

 after there was any human survivor able to understand it, 

 we have to recognise the validity of other records showing 

 that parrots may outlive their long-lived owners and exceed 

 even fourscore years. It was a veteran, belonging to the 

 species Chrysotis amazonica, of which Metchnikoff made 

 a careful post-mortem, with the assistance of Mesnil 

 and Weinberg, and she must have been over eighty when 

 she died. During her declining years the captive was 

 feeble and senile ; but the striking fact was that a thorough 

 investigation of the tissues revealed little, except along 

 one (very important) line, that could be called degenerative 

 or deathful. 



The post-mortem report on the aged parrot informs 

 us that the liver was slightly fatty, but showed no 

 hint of cirrhosis or any other disease ; the kidneys 

 were tending towards fatty degeneration, but showed 



