OLD AGE. 541 



bone (ho osseous substance is destroyed by the g;\nni cells niendoncd 

 above. In the cells of the senile organs just studied the general and 

 essential phenomena consist, then, in the destruction of parts useful to 

 the organism by wandering cells that present some (raits in conuuon 

 ■with each other. They are voracious cells belonging to the category 

 of elements designated under the generic name of macrophages. Cer- 

 tain macrophages remove the pigment of the hair, certain others 

 destroy the osseous lamelhv, others still devour the contractile sub- 

 stance of muscles. 



It is easy to prove that this activity or rather sup(>ractivity of the 

 macrophages is observed in the most diverse organs of the aged. It 

 is found in the brain, where the cells are in the act of devouring the 

 most noble elements of our organism. In the kidneys and the liver of 

 old persons there are found collections of macrophages that cause the 

 secretory cells of those organs to disappear, thus occasioning phenom- 

 ena of atrophy of very great im])()rtance. 



After having destroyed the noble elements of the aging organism, 

 such as the nervous, renal, and hepatic cells, the macrophages become 

 fixed in place and are transformed into connective tissue without 

 ever being able to su])ply the place of the precious elements that 

 have disappeared. It is in this way that there is set up in the aged 

 that main factor of our premature decay, sclerosis of the organs. A 

 study of the special phenomena of old age shows, then, that they 

 arise from a cellular activity that brings about the destructi;'n of 

 the noble elements and the superiority of the macrophages. The 

 latter, which in a normal state act as protectors of the organism against 

 the invasion of microbes, at last themselves invade the most useful 

 parts. There is produced in our body by the advance of age some- 

 thing analogous to what occurs in the old age of certain peoples when 

 the army, intended to protect the state against exterior enemies, turns 

 against the citizens of its own country. 



In this invasion of the senile organs by the macrophages there 

 sometimes occurs a veritable struggle between these voracious cells 

 and our noble elements. Weakened by diverse causes these elements 

 show signs of degeneration in the form of deposits of fat or of pig- 

 ment. In these conditions of inferiority the cells of the brain, of the 

 kidney, or of the liver more readily become a prey to the macrophages, 

 whence results the loss of intelligence and the disorders of digestion 

 and of the emunctories which are so common among old people. 



But in other cases there can not be any serious question of a struggle 

 between two categories of living elements. AMien the macrophages 

 devour the pigment of the haii-, or, indeed, destroy the osseous sub- 

 stance, there occurs rather an aggression of the macrophages upon 

 inert parts that are incapalile of defending themselves. 



We have tried to show that tlie theory of the mechanism of old age 



