732 PHYSIOLOGY 



bodily superiority In their harder struggle for food amidst more 

 inclement surroundings, have been perforce obliged to satisfy their 

 energy requirements at the expense of animal food. In these days 

 when the products of all climes are at the disposal of civilised man, 

 his food-supply is no longer dependent on the country in which he 

 lives, and it is possible to regulate the composition of his food according 

 to the results of physiological experience. Since the proteins repre- 

 sent the most costly constituents of the food, it becomes important to 

 inquire how much of this class of food-stuffs is essential to the main- 

 tenance of health and whether any advantage is given by taking 

 proteins in excess of the physiological minimum. The fact that 

 those nations which hold the highest place in the world are mainly 

 flesh-eaters cannot be regarded as any proof of the advantage of a 

 flesh diet over a diet poorer in protein. It is the hard struggle for 

 existence which in the northern races has eliminated the weakling 

 and resulted in the production of a superior race. The fact that 

 he is a flesh-eater can also be ascribed to the exigencies of climate 

 and does not necessarily prove that a large flesh diet is responsible 

 for his greater efficiency. 



Of late years a number of careful experiments have been made 

 to determine the minimum amount of protein which must be present 

 in the daily ration of man. I have mentioned above two experiments 

 in which nitrogenous equilibrium was obtained with much smaller 

 amounts of protein than those given in the normal diets. In these 

 experiments, in one of which the man received 43*5 grm. of protein 

 daily, and in the other only 33 grm. of protein, it was found necessary 

 to give at the same time amounts of carbohydrates and fats far 

 exceeding those in the normal diet, so that whereas, e.g. the normal 

 individual takes in between 32 and 35 calories per kilo, the man 

 on 43'5 grm. of protein needed 47'5 calories per kilo, and the one on 

 33 grm. of protein needed the huge amount of 78*5 calories per kilo. 



Other experimenters have, however, succeeeded in maintaining 

 perfect health and nitrogenous equilibrium for a considerable time 

 on a diet containing a much smaller amount of protein than has 

 been generally considered necessary without adding to the ration 

 abnormal quantities of fats or carbohydrates. Thus Siven, in an 

 experiment on himself, found that he could maintain nitrogenous 

 equilibrium for thirty-two days on a diet containing only 6*26 grm. 

 of nitrogen. The total heat-value of the food per day was only 2444 

 calories. Folin, in individuals with an insufficient amount of protein 

 containing only 2*1 to 2 '4 grm. of nitrogen, found that the nitrogen 

 output per diem was only 3 to 4 grm. It would seem therefore 

 that a healthy adult man, having a sufficient intake of non-nitro- 

 genous food, need not metabolise more protein than suffices to yield 



