tr EMICAL COMPOSITION OF FOOD-FISHES. 857 
Speaking roughly, a quart of oysters contains, on the average, about 
the same quantity of actual nutritive substance as a quart of milk, or a 
pound of very lean beef, or a fjound and a half of fresh codfish, or two- 
thirds of a pound of bread. But while the weight of actual nutriment 
in the different quantities of food materials named is very nearly the 
same, the quality is widely different. That of the very lean meat or 
codfish consists mostly of what are called in chemical language protein 
compounds or “ flesh-formers,” the substances which make blood, mus- 
cle, tendon, bone, brain, and other nitrogenous tissues. That of the 
bread contains but little of these, and consists chiefly of starch, with a 
little fat and other compounds which serve the body as fuel and supply 
it with heat and muscular power. The nutritive substance of oysters 
contains considerable of both the “flesh-forming” and the more espe- 
cially heat-and-force giving ingredients. Oysters come nearer to milk 
than almost any other common food material as regards both the 
amounts and the relative proportions of nutrients, and the food values 
of equal weights of milk and oysters, i. e ., their values for supplying the 
body with material to build up its parts, repair its wastes, and furnish 
it with heat and energy, would be pretty nearly the same. But while 
this statement is reasonably correct, the studies thus far made are not 
sufficient to assure us of its absolute accuracy. 
The differences which oystermen observe in the quality of oysters 
from different localities, of different age, and grown under different 
conditions, are made clearer and are to a considerable extent explained 
by chemical analysis. Taking the oysters in the shell, the proportion 
of shell contents, “meat” and “liquor” together, increases relatively 
to the whole weight as the animal grows, at least up to a certain limit. 
In other words a bushel of mature oysters will “ open ” more quarts 
than a bushel of the very young animals. But the differences between 
different kinds, or between specimens of the same kind under different 
conditions, are very wide. 
Taking the edible portion of the oyster, after it has been removed 
from the shell, the differences are much greater than people commonly 
suppose. This is apparent when we compare either the flesh (meats) 
or liquids (liquor) of different specimens, or the whole edible portion, 
the meat and liquor (solids) together. The percentage of water in the 
edible portion of the different specimens of oysters reported in the 
tables beyond varied from 83.4 to 91.4 per cent., and averaged 87.3 per 
cent. This makes the amounts of “ water-free substances,” i. e ., actu- 
ally nutritive ingredients, vary from 16.6 to 8.6, and average 12.7 per 
cent, of the whole weight of the edible portion (shell contents) of the 
animals. In other words the contents of nutritive material in a quart 
(2 pounds) of shell contents (solids) varied from 2f to 5£ ounces. The 
proportion of nutritive substance was twice as large in the one case as 
in the other. 
