654 PHYSIOLOGY 



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 deter- 

 mine the minimum amount of protein which must be present in the daily 

 ration of man. I have mentioned above two experiments in which nitrogen- 

 ous 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 pro- 

 tein, it was found necessary to give at the same time amounts of carbo- 

 hydrates 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, succeeded in maintaining perfect 

 health and nitrogenous equilibrium for a considerable time on a diet con- 

 taining a much smaller amount of protein than has been generally considered 

 necessary without adding to the ration abnormal quantities of fats or carbo- 

 hydrates. 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-nitrogenous food, need 

 not metabolise more protein than suffices to yield 3 to 4 grm. of nitrogen 

 per day, i.e. between 25 to 35 grm. of protein. Other observations have been 

 made on vegetarians, showing that individuals can maintain perfect health 

 on a diet containing only about 34 grm. of protein a day, and with a total 

 calorie value of 1400 to 2000. A series of experiments were conducted by 

 Chittenden with a view to determining how far such a diet is suitable to 

 the average individual, and especially whether it can be continued for long 

 periods of time without interfering with the well-being of the subject of the 

 experiment. The general results of these experiments show that the 

 physiological needs of the body can be met by greatly reduced protein intake 

 with the establishment of continued nitrogenous equilibrium on a far smaller 

 amount of protein food than is contained in the ordinary dietary tables, and 

 that on this diet the individual in some cases, far from suffering in health, 

 has his physical and mental efficiency increased. The experiments were made 

 on various classes of men : instructors and students in the university, 

 soldiers, and athletes. In the case of Chittenden himself the average daily 

 diet contained about 6 grm. of nitrogen and had a heat- value of about 1600 

 calories. In the case of another individual the intake of nitrogen per day was 

 9-5 grm. and the heat- value of the food 2500 calories. It is thus possible 

 to reduce the total energy of the food from about 3300 calories to about 2500 

 calories. "Of the protein taken in by a normal individual therefore a certain 

 amount which is not needed by the organism is at once broken up and serves 



