184 LIFE OF ELIE METCHNIKOFF 



in the connective tissue which supports the hairy 

 scalp. As the pigment becomes destroyed, the hair 

 loses its colour and whitens. The cells which devour 

 the pigment — pigmentophages — ^belong to the cate- 

 gory of macrophages which, in general, absorb all the 

 enfeebled cells in the organism. 



Metchnikofi was able to note similar phenomena 

 in divers other senile atrophies either by his own 

 ulterior researches or by collaboration with his pupils 

 (MM. Salimbeni and Weinberg). 



In the same way that the whitening of the hair 

 depends on the destruction of pigment by pigmento- 

 phages, the wrinkles of the skin, weakness of the 

 muscles, friability of the bones, and senile degeneres- 

 cence of divers organs are caused by the destruction 

 of weakened cells which do not defend themselves 

 and thus become the prey of the stronger and more 

 resisting macrophages. Senility is thus no other than 

 a generalised atrophy. What is it that provokes it ? 

 The answer is : The swarming microbes in our large 

 intestine. They form the permanent source of a 

 slow poisoning of our organism. This fact alone 

 sufi&ces to explain one of the principal causes of the 

 enfeebling of our tissues. It is not simultaneous in 

 all the cells because of their different powers of 

 resistance. The struggle and destruction of the weak 

 by the strong is the cruel law of nature ; therefore 

 the macrophages, more resisting to poisons, take 

 advantage of the weakening of other cells in order 

 to devour them, and this is one of the causes of 

 senility. 



These reflections and the biological researches which 

 confirmed them allowed Metchnikofi gradually to 

 build up a philosophical doctrine, which he ex- 



