NATURE AND DESTINATION OF FOOD. 105 



latter. Again, the Esquimaux and other dwellers upon the Arctic seas find 

 in the bodies of the whales, seals, etc., whereon they subsist, that special 

 supply of the very best combustive material, which alone can enable them 

 to maintain their existence in a climate where the thermometer is for many 

 weeks or months in the year at -40 or even lower, and where the amount 

 of heat which must be generated within the body is four or five times that 

 for which a diet of bread will suffice. On the other hand, the general ex- 

 perience of the inhabitants of warm climates seems in favor of a diet chiefly 

 or entirely vegetable; and its peculiar suitableness appears to consist in its 

 affording an adequate supply of the plastic alimentary substances, in com- 

 bination with farinaceous matters that give the requisite bulk to the food, 

 without affording more combustive material than the system requires, the 

 quantity of starch which undergoes conversion, and which is introduced as 

 sugar into the circulation, being apparently governed rather by the demands 

 of the respiratory process than by the amount ingested ; and the remainder 

 being voided again unchanged. 



64. In a well-arranged system of diet, the proportion that the non-azotized 

 substances ought to bear to the azotized should be determined by the pro- 

 portion of Carbon and Nitrogen which- are eliminated in the excreta of a 

 healthy man in a given period. Now we know from various experiments 

 that with active exertion about 800 grains of Nitrogen and 4600 grains of 

 Carbon are daily discharged by the several channels of the lungs, skin, kid- 

 neys, and bowels; the proportion of the Nitrogen to the Carbon eliminated 

 being, therefore, nearly as 1 : 15. Now, if we compare the composition of 

 bread and of meat, we shall see what is their relative value as aliments, by 

 the proportion which the C holds to the N. According to Payen, 1 1000 

 grains of Bread contain, in round numbers, 300 of Carbon, and 10 of Nitro- 

 gen ; hence, to obtain the 300 grains of Nitrogen required by the system, 

 30,000 grains (or more than 4 Ibs.) of Bread must be consumed; but the 

 4600 grains of Carbon required are contained in 15,000 grains of Bread; so 

 that to obtain the requisite supply of Nitrogen a quantity of Bread must be 

 consumed containing exactly double the quantity of Carbon required. 

 Hence it is advantageous to add to a bread diet a small quantity of Cheese 

 or other highly nitrogenous food. Again, in the case of Meat, 1000 grains 

 contain 100 of Carbon and 30 of Nitrogen; therefore to obtain the 4600 

 grains of Carbon, no less than 6^ Ibs. must be consumed, whilst the requisite 

 300 grains of Nitrogen are contained in 1^ Ib. of Meat; consequently three 

 or four times more meat must be consumed to supply the Carbon than is 

 necessary to furnish the Nitrogen. Here then we see again the economy of 

 the mixed diet which is so generally employed by Man, whether in a barbar- 

 ous or highly-civilized state; and the following table will show how an ad- 

 mixture of bread and meat would require a much less consumption of both, 

 than if each were taken separately: 



Graius of Carbon. Grains of Nitrogen. 



15,440 grains of Bread contain . . . 4(130 . . 154 

 4, G30 grains of Meat contain . . . 463 . . 154 



5093 . . 308 



Thus about 2 Ibs. of bread and |- Ib. of meat are amply sufficient to 

 compensate the daily losses of the system of a healthy man. 2 Hence we 



1 Des Substances Alimentaires, Paris, 1854. 



2 See Beelard, Traite Elementaire d Physiologie, p. 570 ct scq. 18G2. G. Meyer 

 (Zeits. f. Biol , Band vii, Heft 1) has made a series of interesting observations on- the 

 effects of exclusive bread diet on man and dogs. White bread furnished a smaller 



8 



