138 METABOLISM AND NUTRITION 



whether the foodstuffs contained in the different articles of food are utilized 

 in the intestine to an equal extent. Experiment has shown that as a matter 

 of fact the utilization of the foodstuffs in different articles of food and 

 "dishes" is very different (Rubner). For the method of these investigations 

 and the share which the intestine has in the formation of the fasces, see 

 pages 85 and 96, also Chapter VII. 



1. UTILIZATION OF THE FOODSTUFFS 



A. PROTEID 



We have already seen that the quantity of N in the faeces which comes 

 from the body itself, and therefore represents a product of metabolism > 

 amounts to 0.5-1.4 g. per day. If then we find only this quantity of nitro- 

 gen in the faeces after a certain diet, we may say that the ingested nitrogen 

 has all been utilized. 



This is generally the case with animal foods. In experiments with meat, 

 fish, eggs, milk and cheese, the daily elimination of N in the faeces varies 

 from 0.14 to 1.9 g. ; only in one case with 4,100 g. of milk do we find in 

 the literature of this subject a greater quantity (3.1 g.) of N in the faeces. 

 If the total N in the fa3ces be calculated as lost from the N ingested, it 

 amounts to only 2.0-7.7 per cent. 



Kermauner has taken the pains to estimate quantitatively the residue of 

 meat recognizable as such in the faeces of three individuals, and has found that 

 after an ingestion of 266 g. meat per day the highest amount in the faBces was 

 4.7 g. and the lowest 0.3 g. (=0.16 and 0.01 g. N respectively). 



With vegetable foods the quantity of N in the faeces is considerably greater, 

 and in certain experiments has been known to reach the high value of 9.09 g. 

 per day; the loss in this case amounts to as much as forty-eight per cent and 

 as a rule is more than fifteen per cent. 



This is due primarily to the fact that vegetable foods contain nitrogenous 

 compounds in their husks, coats, etc., which are not proteid and are not digested 

 in the intestine. The more husk, etc., a vegetable food contains, the less favor- 

 ably does the utilization of its nitrogen prove to be. For this reason we find 

 in the faaces from rye bread made from whole meal 2-4 g. nitrogen, represent- 

 ing a loss of thirty to forty per cent. If, on the other hand, most of the bran 

 be removed, the utilization appears more favorable with a loss, namely, of only 

 2 g. N or ten to twenty per cent. Other factors tending to make the utilization 

 of coarse vegetable foods less favorable are their relative bulkiness, the acid 

 fermentation of the carbohydrates, and the percentage of indigestible substances. 

 All these conditions tend to stimulate the musculature of the intestine and thus 

 to produce a more rapid evacuation of the intestinal contents. 



B. UTILIZATION OF FAT AND CARBOHYDRATES 



The daily faeces from a diet which contains no fat will lose 3-7 g. by 

 extraction with ether. If, therefore, the faeces after ingestion of a certain 

 fat contain no more fat than this, we can say that that particular fat has 



