MINIMAL A MO UNT OF PROTEID IN FOOD. 8 7 5 
therefore, 3000 kilo-calories may be taken as a fair average for the caloric 
value of the ingesta of a man weighing about 70 kilos., which would give 
about 43 calories for each kilogram body weight. 1 
In women the amount is somewhat less than this, both absolutely and also 
relatively. In children, though absolutely less, it is relatively greater. 
Since the combustion of 1 grm. fat produces 9'3 kilo-calories, and the 
combustion of 1 grm. proteid to urea C0 2 and H 2 and of 1 grm. starch 
in I !0 2 each produces 41 kilu-calories, the combustion of 100 grins, fat 
will produce an equal amount of energy with the combustion of 227 grins., 
either of proteid or of starch. This amount, therefore, of proteid or of 
starch is said to be of the same " isodynamic value" as 100 grins, fat. 
It has been shown by the carefully conducted calorimetric investigations 
of Eubner, 2 that the isodynamic values are as nearly as possible the 
same, whether the combustion occurs in air, or in the tissues of the 
animal body. 3 
Minimal amount of proteid necessary in food. — There has been 
much disputation as to the minimal amount of proteid which it is 
possible for a man in health and doing work to take in his diet in the 
course of twenty-four hours. Eanke gave as a normal diet for an 
average man (70 kilos.) not engaged in muscular work, 100 grms. of 
proteid, 100 grms. of fat, and 240 grms. of carbohydrate. 4 Voit 
allowed for a man of 70 to 75 kilos., doing ten hours' muscular 
work, 118 grms. of proteid, 56 grms. of fat, and 500 grms. of carbo- 
hydrate. 5 It has, however, been shown that, provided the non-proteids 
in the diet are increased — not only in proportion to the caloric value of 
proteid withdrawn, but considerably more than in such proportion — a 
man can maintain equilibrium and can do work upon considerably less 
proteid than that allowed in the diets of Eanke and of Voit. 
Thus Hirschfeld (70 kilos.) found that he could maintain himself for a 
considerable time in perfect health with a diminution of proteid down to 
75 grms., or even for a time down to 49 grms. per diem, but under these 
circumstances it was necessary to increase enormously the amount of non- 
proteid and especially of carbohydrate material taken with the diet. 
1 Hultgren and Lantergren, working with Tigerstedt, found the heat value of the food 
of six persons living on a freely chosen diet to vary from 33 to 49 calories per kilogramme. 
They found that the heat value of the proteid was about lb' to 19 per cent, of the total 
heat value of the food, that of the fat being about 21 to 24 per cent., and that of the 
carbohydrate about 60 per cent, Ranke's diet (vide infra), with a heat value of only 
2,365,000 calories, is for a man performing no muscular work. 
2 Ztschr.f. Biol., Miinchen, 1894, Bd. xxx. S. 73. 
s A more complete account of the heat values of the foodstuffs is given in the article on 
"Animal Heat" in p. 833. For the influence of food on the respiratory exchange, see 
article "Chemistry of Respiration," p. 717; see also Magnus-Levy, Arch. f. d. yes. 
Physiol, Bonn, 1893, Bd. lv. S. 1. 
4 To this may be added 25 grms. salts and 2535 grms. water (including that contained 
in the solid food). These several constituents are contained in a daily ration of 250 grms. 
meat, 400 grms. bread, 70 grms. starch or sugar, 100 grms. fat, 10 grms. salt, and 2100 
water (J. Ranke, " Die Ernahrung des Menschen," Miinchen, 1876). 
5 Such a diet contains about 18 "3 grms. N, and about 328 grins. C, whereas Ranke's 
diet contains about 15-5 grms. X. and about 220 grms. C. It should be added that about 
13 grins, of the 118 grms. proteid of Voit's diet is not absorbed or assimilated, so that the 
available proteid is about 105 grms. This closely corresponds with the results of Bleibtreu 
and Bohland (with Pfliiger), who give 1 '5 grms. per kilo, body-weight. This would be a 
little over 105 grms. for a man weighing 70 kilos. (Arch. f. d. <jes. Physiol., Bonn, 1886, 
Bd. xxxviii. S. 1). In Hultgren and Lantergren's observations the actual amount of the 
ingested proteid which underwent metabolism averaged 101 "3 grms. 
6 Arch. f. cl. ges. Physiol., Bonn, 1887, Bd. xli. S. 533 : and 1889, Bd. xliv. S. 428; 
also Virchow's Archie, 1888, Bd. cxiv. S. 301. 
