INORGANIC FOODS. 371 



end of six or seven days. 1 It takes nine days for dogs to accomplish 

 the same result; at the end of eighteen days the weight was three times 

 that at birth. With cats it requires nine or ten days for the weight 

 to become doubled; in one case the weight was three times as much 

 at the end of 19 days, and four times as much at the end of 29 days. 

 Pigs develop less rapidly. On an average, it requires 14 days for 

 the original weight to be doubled; with sheep 15 days, goats 32 days, 

 calves 47 days, and 60 days in the case of a colt. The slowest devel- 

 opment is shown in the case of the human offspring, which does not double 

 its weight until about six months have passed away. Observations upon 

 the cat show that the rate of development decreases with age. It is 

 particularly striking only at the time of birth. The case of guinea pigs is 

 not without interest. According to their development, they scarcely 

 belong in the ranks of the mammalia; by eating green food shortly after 

 birth, they rapidly increase in weight. At birth they are already remark- 

 ably well developed. Even then they are able to eat the same food as 

 that of the mother, and thrive on cabbage, etc. The female of this animal 

 possesses only two mammary glands, situated in the groin, and milk plays 

 but a subordinate part in the nourishment of the new-born guinea pig. 

 The fact that the first development of these animals takes place quite as 

 rapidly as in the case of the most closely related animals, leads us to the 

 assumption that in early times these animals came into the world in a 

 much more undeveloped condition, and were forced to depend upon milk 

 for nourishment, like other mammalia. 



It has often been suggested that rickets, a quite common children's 

 disease, is caused by a lack of lime-salts in the nourishment. In fact, this 

 disease appears most frequently when the mother's milk for some reason 

 is replaced by some other form of nourishment. There is no doubt that 

 in considering the value of a food for replacing the mother's milk, too 

 much stress has been laid upon the amount of fat, proteid, and carbo- 

 hydrate. Certainly a mistake is being made unless equal attention is paid 

 to the amount of inorganic substances contained in the nourishment. 

 According to general experience, it is not possible to replace the mother's 

 milk satisfactorily by the milk of some other animal. It is necessary to 

 add something to cow's milk in order that there may not be any substance 

 present in less than the proper amount. Then again it is particularly 

 erroneous to judge the value of a food used to replace the mother's milk 

 by its calorific value. We must never forget that the suckling must build 

 up its tissue first of all. It is, therefore, by no means a matter of indiffer- 

 ence whether this or that organic substance is relegated to the background, 

 whether fat or carbohydrate. For the growing suckling, carbohydrates 

 and fat cannot be considered as equivalent in this sense. They are 



1 Abderhalden: Z. physiol. Chem. 26, 487 (1899); 27, 408 and 594 (1899). 



