DEATH 237 



of the heart or of breathing, or of the nervous 

 system, may break down, and death of the 

 body as a whole takes place. The organs, 

 or rather, the tissues in the organs, the cells, 

 the living matter, die more slowly, and at 

 last these too cease to live The organic 

 matter of the body then, under the influence 

 of micro-organisms in the air or the soil, 

 breaks down by processes of putrefaction, 

 and, in course of time, it is decomposed 

 into simpler and simpler organic substances 

 until the ultimate elements are reached. Thus 

 organic matter becomes again inorganic. 



142. The causes of longevity are not under- 

 stood ; nor, as already mentioned, is it evident 

 why the degenerative changes above referred 

 to should come on. Each species of animal, 

 at all events among the higher animals, 

 seems to be so constructed as to have a 

 longevity peculiar to the species. Attempts 

 have been made to connect this in some 

 way with the period of utero-gestation, but 

 little reliance can be placed on such specu- 

 lations. It is clear, however, that longevity 

 is largely a matter of heredity, if accidents 



