DEFENSIVE FERMENTS OF THE ANIMAL ORGANISM 15 



important stages in the nutrition of the young of the 

 mammal. Right up to its birth, which is the first 

 stage, the foetus has received from the mother only 

 food which is in harmony with her body, and it makes 

 this harmonize with its own blood and its own cells. 

 Its organism has never come into contact with entirely 



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disharmonious substances, and thus its metabolic 

 processes run on definitely balanced lines. But birth 

 supervenes, and with it the first change in the mode 

 of nourishment. The individual has become inde- 

 pendent. Respiration begins, and the cells of the 

 lungs immediately enter upon their duty of exchang- 

 ing gases. With equal rapidity the cells and glands 

 of the intestinal walls undertake their new functions, 

 which are, with the help of ferments, to prepare new 

 nourishment for the cells of the body. The mother 

 facilitates this task by giving off a supply of milk 

 that is adapted to the requirements of the infant. In 

 the first place, the intestinal cells have their task 

 simplified. They never come into contact with a con- 

 tinually changing mixture of ions, nor are they over- 

 whelmed with all kinds of disintegrated organic 

 by-products. In this way the as yet inexperienced 

 being is gradually accustomed to its new functions, 



C? <5 



and finds itself at last well prepared when it has to 

 deal with a new kind of food which requires it to exer- 

 cise its functions in a more variable, and, consequently 

 more difficult manner. From the moment of parting 



