

EVOLUTION AND MORTALITY 



2-79 



mortality alone. Now we have at hand 

 in tables z and 4 of the present paper some 

 additional evidence. We see at once that 

 all along the evolutionary pathway, from 

 reptiles to man, the endoderm has had the 

 largest absolute mortality chargeable 

 against it, but the proportionate amount has 

 steadily diminished. It is a possible 



rived from the ectoderm and the meso- 

 derm has increased in the course of evolu- 

 tion. There is, of course, a necessary 

 compensation in this. If 100 per cent of 

 mortality is divided into parts and some of 

 these parts exhibit a secular change, up or 

 down, the other parts must of necessity 

 show a trend in the opposite sense. If 



Mortality 



from. 



Breakdown 



of 



Organs 



Derived 



from 

 Ectoderm 



Man 

 England 



Man 

 Sao Paulo 



Mammals 



Birds 



Reptiles 



Mortality from Breakdown 

 of Organs Derived 

 from 

 Mesoderm 



Mortality from Breakdown 



of Organs Derived 



from 



Endoderm 



91,6 



Fig. 3. The Mortality, per Hundred Deaths prom All Causes, Distributed According to the Primary 

 Germ Layers prom which the Different Organ Systems Develop Embryologically 



inference from the evidence that the organs 

 derived from endoderm have become pro- 

 gressively better adapted to meeting suc- 

 cessfully the environmental stresses and 

 strains which bear upon them in the 

 business of living. 



On the other hand the proportionate 

 mortality assignable to the organs de- 



preventive medicine has in any degree 

 reduced the proportionate number of deaths 

 associated with the endodermal organs, 

 just by so doing it must necessarily have 

 increased the proportionate mortality as- 

 sociated with either ectodermal or meso- 

 dermal organs, or both. But it should 

 not be overlooked that the same trends 



