538 OLD AGE. 



of the senile alterations of our body, it is indispensable that we should 

 study the clianges that occur in the cells that compose it. 



A great number of these elements are continually being lost. From 

 the surface of our epidermis are detached minute scales composed of 

 a quantity of flat desiccated cells that have become incapable of pro- 

 tecting our skin. The secretions of the mucous membranes daily 

 carry away great numbers of the cells that make up those membranes. 

 There is, therefore, a considerable Avear of the microscopic elements of 

 our body which must be reconstituted in order to maintain its equi- 

 librium. 



Under these conditions it was quite natural to ask whether the 

 reparation of our cells is as well effected in the old as in those of 

 adult life. This question arose all the more naturally because there 

 are known examples of very low organisms that multiply Iw division, 

 and which, after a considerable number of generations, finally fall 

 into a state of exhaustion in which reproduction becomes gradually 

 slower and more difficult, and may even cease altogether. This state 

 of debility, which has been compared to senile atrophy, yields to cer- 

 tain influences, such as the conjugation of two exhausted individuals, 

 or even to improved nourishment. 



But since among inferior organisms, which resemble so much the 

 cellular elements of our body, reproduction becomes exhausted at the 

 end of a certain period, we are led to suppose that the same law may 

 also apply to the senile atrophy of our own organism. Therefore, 

 numerous scientists affirm that old age finally results because it is 

 impossible for an organism to repair the cellular losses by the forma- 

 tion of a sufficient number of new elements — that is to sa}^, because of 

 the exhaustion of the reproductive faculty. 



One of the scientists who have more especially concerned them- 

 selves with general questions, Weismann, expresses himself on this 

 subject in a very categorical manner. According to him, the senile 

 degeneration that ends in death does not depend on the wearing away 

 of the cells of our organism but rather upon the fact that cellular 

 proliferation, being limited, becomes insufficient to repair that loss. 

 As old age appears in different species and ditterent individuals at 

 various ages, Weismann concludes that the number of generations 

 that a cell is capable of producing differs in different cases. It is, how- 

 Qver, impossible for him to explain win', in one example, cellular mul- 

 tiplication may stop at a certain figure, while in another it maj go 

 much further. 



This theory appears so plausible that no attempt has been made 

 to support it by precise facts. We even see, in the most recent 

 attempt at a theory of old age, by Doctor Biihler, the thesis of the 

 exhaustion of the i-eproductive power of the cells accepted and devel- 

 oped without sufHcient discussion. It can not be denied that it is 



