822 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
calories. The calorie is the heat which would raise a kilogramme of 
water 1° 0. (or 1 pound of water about 4° Fahr.). A foot-ton is the 
energy (power) which would lift 1 ton 1 foot. One calorie corresponds 
to 1.53 foot-tons. A gramme of protein or a gramme of carbohydrates 
is assumed to yield 4.1, and a gramme of fats 9.3 calories. A given 
weight of fats is thus taken to be equivalent, in fuel value, on the aver- 
age, to a little over twice the same weight of protein or carbohydrates. 
The figures for potential energy in Table i are calculated for each food 
material by multiplying the number of grammes of protein and of 
carbohydrates in 1 pound (1 pound equals 453.6 grammes) by 4J, and 
the number of grammes of fat by 9.3, and taking the sum of these three 
products as the number of calories of potential energy in a pound of 
the material.* 
I have not applied these methods of calculation to shellfish in this 
article, because the nature of the compounds which make up their 
nutritive ingredients is not fully understood, and it is not certain that 
what we call protein, fats, and carbohydrates in them have the same fuel 
value as in meats, fish, etc. For the same reason I have not attempted 
detailed estimates of the pecuniary economy of shellfish as compared 
with other food materials.! 
The result of analyses of food material can be stated in a variety of 
w r ays. That followed in Tables i and in, beyond, may be explained 
by an example. 
The flesh or edible portion of a specimen of beef sirloin, of medium 
fatness, was analyzed and found to contain, approximately — water, 60 
percent.; protein, 19 per cent.; fats, 20 per cent.; mineral matters, 1 per 
cent. These, then, are the percentages of water and nutrients in the 
edible portion of the meat. But when we buy our sirloin steak or roast 
by the pound, as we ordinarily do, we get not only the flesh, the edible 
substance, but with it more or less bone, sinew, and other refuse matter. 
This specimen contained about one-fourth, or 25 per cent., of bone, and 
three-fourths, or 75 per cent., of flesh. If, then, we are to consider the 
composition of the meat as we buy it, we must take the refuse matters 
into account. The proportions of the several ingredients in both the 
edible portion and the whole piece above referred to may be stated thus: 
Constituents. 
In flesh, 
edible 
portion. 
In meat 
as bought, 
including 
refuse. 
Refuse, bones, etc 
Per cent. 
None. 
60 
19 
20 
1 
Per cent. 
25 
45 
Mi 
15 
Of 
Water 
Protein 
Mineral matters 
Total 
100 
100 
* See “The Potential Energy of Food,” in the Century Magazine for July, 1687- 
t See article on “ Pecuniary Ecouomy of Food,” in the Century Magazine for Jan- 
uary, 1888. 
