262 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [32] 
chemical composition of a food material what is its value as compared 
with other foods for nourishment. The bulk of the best investigation 
of this subject has been made in Germany, where chemists and physi- 
ologists have already got so far as to feel themselves warranted in com- 
puting the nutritive values of foods and arranging them in tables, which 
are coming into popular use. 
As this may fall into the hands of some readers not entirely familiar 
with the latest developments of the chemistry of food and nutrition, I~ 
may be permitted to cite a few explanatory statements from a paper 
read before the American Fish Cultural Association.* 
THE NUTRIENTS OF FOODS. 
We eat meat and fish, milk and bread, to build up our bodies, to repair their wastes, 
to supply heat, to keep ourselves warm, and strength with which to work. This is 
the common way of putting it. Speaking as chemists and physiologists, we should 
say that our food supplies, besides mineral substances and water, albuminoids, car- 
bohydrates, and fats, whose functions are to be transformed into the tissues and fluids 
of the body, muscle and fat, blood and bone, and by their consumption to produce 
heat and force. 
Albuminoids occur in plants, as in the gluten of wheat; and in the animal body, as 
in the fibrinogen and fibrinoplastic substances of blood, in the fibrin of muscle, in 
albumen (white) of eggs, and in the casein (curd) of milk. 
The albuminoids are the most important of the nutrients of foods. Not only do they 
share in the formation of the fatty tissues and in the supply of material for the pro- 
duction of animal heat and muscular power, thus performing all of the functions of 
the other food ingredients in the body, but they also have a work of their own in the 
building up of the nitrogenous tissues, muscles, tendons, cartilage, &c., in which 
none of the other ingredients can share. 
The carbohydrates, of which we have familiar examples in sugar, starch, and cellu- 
lose, differ from the albuminoids in that they have no nitrogen. They have, accord- 
ing to the best experimental evidence, no share in the formation of nitrogenous tissues 
in the body. It is hardly probable that they are transferred into fats to any con- 
siderable extent ; their chief use in food seems to be to supply fuel for the production 
of animal heat, and very probably of muscular power. They are very important 
constituents of foods, but much lessso than the albuminoids and fats. They occur in 
only minute proportion in meats, fish, and like animal foods. 
The fats are familiar to us in the forms of vegetable fats and oils, like linseed and 
olive oils, in fat meat, tallow, and lard, and in butter. The fats, like the carbohy- 
drates, are destitute of nitrogen. The fats of the food are stored in the body as fats, 
transformed into carbohydrates, and serve for fuel, but do not form nitrogenous tissue. 
They are more valuable than the carbohydrates, because richer in carbon and hydro- 
gen, the elements which give vaiue to fuel, and because they supply the body with 
fats. 
In brief, the albuminoids, the nitrogenous constituents of foods (albumen, fibrin, 
&c.), which make the lean meat, the muscle, the connective tissues, skin, and so on, 
are the most important of the nutrients. Next in importance come the fats, and last 
the carbohydrates—sugar, starch, and the like. One reason of the inferior position 
of the carbohydrates is the fact that they have nonitrogen. The albuminoids can do 
their own work and all the work of the carbohydrates and the fats as well, while these 
latter can only do their own. With albuminoids alone we might make a shift to get 
on for a good while, but with carbohydrates and fats alone we should speedily starve. 
*See Reports of Am. Fish Cult. Ass’n., 1880 and 1881. 
