142 BIOLOGY OF DEATH 



the process of evolution is least able to meet successfully 

 the vicissitudes of the environment. The ectoderm has 

 changed most in the course of evolution. Of this the cen- 

 tral nervous system of man is the best proof. There 

 have also been formed in the process of differentiation, 

 protective mechanisms, the skull and vertebral column, 

 which very well keep the delicate and highly organized 

 central nervous system away from direct contact with 

 the environment. The skin also exhibits many differen- 

 tiations of a highly adaptive nature to resist environmen- 

 tal difficulties. It is then not surprising that the organ 

 systems developed from the ectoderm break down and 

 lead to death less frequently than any other. The fig- 

 ures make it clear that man's greatest enemy is his own 

 endoderm. Evolutionally speaking, it is a very old- 

 fashioned and out-of-date ancestral relic, which causes him 

 an infinity of trouble. Practically all public health ac- 

 tivities are directed towards overcoming the difficulties 

 which arise because man carries about this antediluvian 

 sort of endoderm. We endeavor to modify the environ- 

 ment, and soften its asperities down to the point where 

 our own inefficient endodermal mechanism can cope with 

 them, by such methods as preventing bacterial contam- 

 ination of water, food and the like, warming the air we 

 breathe, etc. But our ectoderm requires no such exten- 

 sive amelioration of the environment. There are at most 

 only a very few, if any, germs which can gain entrance to 

 the body through the normal, healthy unbroken skin. 

 We do, to be sure, wear clothes. But it is at least a debat- 

 able question whether, upon many parts of the earth's 

 surface, we should not be better off without them from 

 the point of view of health. 



These data indicate further in another manner how 



