GROWTH AND CHEMICAL PURITY 275 



ing the period of fetal growth. The female therefore 

 would have an increasing chemical difference to over- 

 come. We have seen that the standard of chemical 

 purity of the body is maintained through the action of 

 the kinetic system. When there is a chemical difference 

 between the growing fetus and placenta, therefore, the 

 kinetic system of the mother would be activated exactly 

 as when any other foreign protein is present in her 

 body. An added increase in the work of the kinetic 

 system would be imposed. Also, the increase in metab- 

 olism required for the growth and activity of the 

 fetus would give an increased production of acid by- 

 products as a result of the increased energy transfor- 

 mation. That the needs of the fetus are considerable 

 is shown by the fact that during pregnancy the total food 

 intake of the mother is greatly increased. As a result 

 of this increased intake of food, the elaboration of 

 material for the growth of the fetus, and the added 

 burden of overcoming the difference in chemical 

 standards, the kinetic system of the pregnant mother 

 should and does exhibit greatly increased activity, as 

 is shown by the following evidence : 



Brain: In the pregnant state there is progressive 

 loss of muscular power, mental efficiency and resistance 

 to infection. Memory, reason and endurance suffer 

 just as they do in infection or in auto-intoxication. 

 More direct evidence of the effect of pregnancy on 

 the brain was found by examining the brain-cells of 

 pregnant rabbits and cats. In our histologic studies of 

 normal pregnancy we found evidence of brain over- 

 work and brain deterioration. The percentage of hypo- 

 chromatic brain-cells was above normal. In addition 



