[27] NtJTRITIVE VALUE OF FISH AND INVERTEBRATES, 459 



shall see further, in examining the pecuniary cost, protein is the dear- 

 est as well as most important of the ingredients of foods. 

 ' Experiments and observation have led to the assumption that the 

 minimum proportions of the several classes of nutrients required per 

 day by an ordinary man, doing moderate manual labor, would be, on 

 the average: Protein, 118 grams (4.2 ounces) j fats, 56 grams (2 ounces); 

 carbohydrates, 600 grams (17.G ounces). 



Of course, the food actually consumed by people in different conditions 

 of life varies widely in composition as well as amount. The food of peo- 

 ple in good circumstances generally contains larger, and the food of 

 the poor, smaller, proportions of protein than the above standard re- 

 quires. 



The same experimental research which has revealed to us the ways 

 in which our food supplies our bodily wants, has shown us how to es- 

 timate the relative nutritive values of different foods from their chemi- 

 cal composition. The estimates are only approximate, because the nu- 

 tritive effects are influenced by various conditions, some of which re- 

 search has not yet definitely explained, while others vary with the 

 nature of the food or of the user, so that the value of a given food in a 

 given case may vary from the standard set by the analysis. These 

 sources of uncertainty are nevertheless so narrowed down by late in- 

 vestigation, and the errors confined within such limits, that by intelli- 

 gent use of the facts at our disposal we may judge very closely from 

 the chemical composition of a food what is its value as compared with 

 others of the same class, at any rate, for our nourishment. 



CHEMICAL ANALYSIS OF FOODS. 



Tables XI and XII, beyond, give the composition of a number of the 

 more important kinds of animal and vegetable foods. The details will 

 perhaps be best explained by an example. A sample of beef, sirloin, 

 of medium fatness, was found to consist of about one-fourth bone and 

 three-fourths flesh, edible substance. The flesh was analyzed and found 

 to contain, nearly: water, 60 per cent.; protein, 19 -pev cent.; fats, 20 

 per cent.; mineral matters, 1 per cent. Calculated upon tlie Avhole 

 sample of meat, of wliich one-fourth, or 25 per cent., was bone and other 

 refuse, aud 75 per cent, flesh, the analysis would stand as in the sched- 

 ule below, in which the composition of the flesh by itself and that of 

 the meat, bone, and aU, are both given : 



