ON THE BALANCE OF THE VITAL ECONOMY. 425 



Egesta. This excess is believed by Pettenkofer and Voit to be attributable 

 to a slight excretion of water, which is rendered probable because the excess 

 of oxygen and hydrogen is in the proportion in which they form water, ;m<l 

 because if from the actual body weight the mean daily quantity of f;rrr> 

 were deducted, there was an actual diminution in the weight of the animal 

 amounting to 34 grammes. The minus quantity of 3.8 grammes of Carbon 

 they attribute to a small production of fat from the meat. Numerous ex- 

 periments of a similar nature have been made on the same principle on man 

 and animals by Petteukofer and Voit. The principal source of error in ex- 

 periments conducted in this manner lies in the analysis of the flesh admin- 

 istered as food, especially in regard to the nitrogen which it contains. The 

 estimate here taken was that of Voit, 1 who considered it to contain 3.4 per 

 cent, of nitrogen ; but other observers 2 have found that the proportion 

 varies in the flesh of different animals, or when the composition of the flesh is 

 determined by different methods of analysis, from 2.14 to 5.17 per cent., so 

 that a surplus or a deficit of nitrogen would be found in the excreta accord- 

 ing as the one or the other estimate is taken as the average. Another diffi- 

 culty is in the analysis of the fteces, especially when the experiment is made 

 on one of the Herbivora or on an omnivorous animal, on account of the 

 large amount of indigestible material they contain. In the Carnivora, on 

 the other hand, the amount of indigestible substances is insignificant. Thus 

 in cats it does not exceed 1 per cent. (Bidder and Schmidt). In man it 

 amounts to 4-8 per cent. (Valentin, Barral, Hildesheim), in the pig 19.9 

 per cent. (Boussingault), in the cow 34.4 per cent. (Boussiugault), and in 

 the horse 40-50 per cent. (Valentin). 



338. Balance of the Economy in Fasting. Great interest attaches to the 

 study of the excreta during inanition, for we may be sure from the care that 

 we elsewhere see to be taken by nature in the preservation of life, that the 

 animal then lives most economically, for it is in fact living upon its own 

 tissues, and no more is consumed than is absolutely requisite for the main- 

 tenance of the internal work of the body, which becomes greatly reduced 

 in amount, whilst after the first day or two there is little disposition to ex- 

 ternal work. The chief objection to this method of determining the min- 

 imum quantity of food required, and the minimum amount of Egesta dis- 

 charged from the body is, that soon after the withdrawal of all supplies the 

 activity of the principal organs, as the liver, pancreas, spleen, glands of 

 intestine, etc., undergoes material diminution. The diminution in the general 

 weight of the body and of the several excreta, begins on the very first day 

 of fasting, and continues throughout, though of course, in consequence of 

 the progressively smaller bulk of the body in a gradually lessening propor- 

 tion. The most marked alteration in the excreta occurs in the Herbivora, 

 since in fasting they live on themselves ; in other words, change from a 

 vegetable to an animal diet, and the urine consequently contains for a time 

 an increased proportion of nitrogen. Both in these animals, however, and in 

 carnivora, the amount of urea gradually diminishes with the diminished 

 bulk and lessened external and internal activities. Well-fed animals bear 

 inanition for a longer period than ill-fed ones lean young pigeons dying in 

 three days, and after a loss of only a fourth of their weight, whilst old, 

 well-nourished ones live for thirteen days, and do not die till their weight is 

 reduced to one-half. The loss of weight falls very unevenly on different 



1 Voit, Zeits. f. Biologic, Bd. i, p. 100. 



2 Nowak, Lcube, Siewert, Petersen, Kitthausen, Zeitschrift f. Biologic, Bd. vii, 

 1871. Seegen, Wien. Akad. Anzeiger, 1870, p. 230. Schenk, Sitzungsber. d. k. 

 Akad. zu Wien., Jan. 1870. 



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