268 PRINCIPLES OF GENERAL PHYSIOLOGY 



the nitrogen output in the urine of seven of us who were working in the 

 Physiological Laboratory of University College, London, at that time. No 

 alteration was made in our occupations nor in the food taken, except that a 

 dinner of the Physiological Society occurred on one day, which tended to 

 increase the general average. The values obtained were from 0-16 to 0'2 g. 

 of nitrogen per kilogram of body weight, or an average of 13*5 g. per individual, 

 equivalent to 93 g. of protein ; a value only three-quarters of that given by Voit, 

 although rather more than twice that regarded by Chittenden as adequate. 



A point of interest is that in Rowntree's " Poverty, a Study in Town Life," the author has 

 adopted Atwater's standard of 125 g. as the minimum protein and consequently finds that 

 27 per cent, of the population of York are living in poverty, because their protein consumption 

 is below this figure. Jn point of fact, the lowest value found was 89 g. , very little below that 

 of the lalxiratory workers, and this applied only to those whose weekly wage was lwlo\\ 

 twenty-six shillings. Caution must then be exercised in drawing conclusions as to social 

 conditions from protein consumption. One would have to conclude that physiologists as a 

 class are living in poverty. 



Cathcart (1912, p. 69) regards 90 g. of protein as an average value, from his own 

 experience. This author's discussion of the question will be found on pp. 66 to 72 of his 

 monograph (1912). We may note that Siven (1901) found it possible to maintain nitrogen 

 equilibrium on 4 '52 g. of nitrogen (=28'3 g. of protein) per day. But there seems some 

 evidence that continued existence on so low a protein diet may entail low resistance to 

 external influences, such as infection, although this effect is by no means clearly made out and 

 the results of Hindhede, to be given immediately, show that it is not necessarily the case. 



The degree of activity of the organism is naturally to be taken into account. 

 We may recall M'Collum's experiments on pigs (1911), in which the total 

 nitrogen required for maintenance appears to be only 2'6 g. for a pig of about 

 the weight of a man. 



The recent work of Hindhede (1913) affords some valuable data on the question 

 before us. In his experiments, care was taken that the total calorie value of 

 the food was abundant, a point of essential importance, as Cathcart points out 

 (1912, p. 70), and not sufficiently ensured in some of the experiments of Chittenden, 

 in which it was too low. A further point of importance in Hindhede's experiments 

 is that they were continued for a considerable time. A strong, healthy young 

 man of t 70 kg. weight, a laboratory servant in the Nutrition Institute of 

 Copenhagen, was the chief subject. It was found that, while continuing to 

 perform all his usual duties, he was able to live on a diet consisting only of 

 potatoes, apparently new potatoes, together with margarine and a little onion for 

 flavour, and containing, on the average, only 4 -425 g. of nitrogen per day. This 

 experiment lasted 178 days and although 75 g. of nitrogen had actually been lost 

 from the body, it was not possible to discover that the subject was otherwise 

 in any different condition than at the beginning of the period. From the figures 

 given, it appears that he was in nitrogen equilibrium during the actual time on 

 which this diet was taken, and that the loss of nitrogen occurred in one or two 

 short periods in which less nitrogen was taken, owing to replacement of the 

 greater part of the potatoes by fruit. During the 1 50 days on which the potato diet 

 was taken, nitrogen equilibrium was present on 5 g. of nitrogen per day. Taking 

 one particular period of nineteen days, in which all the conditions were especially 

 satisfactory, nitrogen equilibrium was maintained on only 3 '5 g. per day. It is 

 to be remembered that, on this potato diet, which seems to be the only one which 

 can be put up with for so long a time, it was impossible to reduce the nitrogen 

 further without diminishing the calorie value below that which was found to be 

 essential, namely 4,000 calories per day. We may remark also that the method of 

 cooking the food was found to be a matter of great importance, so that it should 

 be sufficiently palatable to be taken with relish in large enough quantities to 

 give the calorie value required, in fact, about 2-2 to 3-5 km., according to the 

 severity of the work done. To assign proper value to the experiments, it is 

 pointed out that the subject was really more than an ordinary laboratory servant ; 

 he performed the duties of an assistant, working fourteen to sixteen hours a day, 

 extremely active and taking great interest, not only in the experiments described, 

 but also in the work as a whole. We may note the high calorie value of the diet ; 

 that given by Voit for soldiers in war-time had an energy value of only 3,575 



