COMPARISON OF FISH WITH MEAT.--In general, the composition of fish is similar to that of meat, for both of them are high-protein foods. However, some varieties of fish contain large quantities of fat and others contain very little of this substance, so the food value of the different kinds varies greatly. As in the case of meat, fish is lacking in carbohydrate. Because of the close similarity between these two foods, fish is a very desirable substitute for meat. In fact, fish is in some respects a better food than meat, but it cannot be used so continuously as meat without becoming monotonous; that is to say, a person will grow tired of fish much more quickly than of most meats. The similarity between the composition of fish and that of meat has much to do with regulating the price of these protein foods, which, as has already been learned, are the highest priced foods on the market.

PROTEIN IN FISH.--In fish, as well as in shell fish, a very large proportion of the food substances present is protein. This proportion varies with the quantity of water, bone, and refuse that the particular food contains, and with the physical structure of the food. In fresh fish, the percentage of this material varies from 6 to 17 per cent. The structure of fish is very similar to that of meat, as the flesh is composed of tiny hollow fibers containing extractives, in which are dissolved mineral salts and various other materials. The quantity of extractives found in these foods, however, is less than that found in meat. Fish extracts of any kind, such as clam juice, oyster juice, etc., are similar in their composition to any of the extractives of meat, differing only in the kind and proportions. In addition to the muscle fibers of fish, which are, of course, composed of protein, fish contains a small quantity of albumin, just as meat does. It is the protein material in fish, as well as in shell fish, that is responsible for its very rapid decomposition.

The application of heat has the same effect on the protein of fish as it has on that of meat, fowl, and other animal tissues. Consequently, the same principles of cookery apply to both the retention and the extraction of flavor.

FAT IN FISH.--The percentage of fat in fish varies from less than 1 per cent. in some cases to a trifle more than 14 per cent. in others, but this high percentage is rare, as the average fish probably does not exceed from 3 to 6 or 7 per cent. of fat. This variation affects the total food value proportionately. The varieties of fish that contain the most fat deteriorate most rapidly and withstand transportation the least well, so that when these are secured in large quantities they are usually canned or preserved in some manner. Fish containing a large amount of fat, such as salmon, turbot, eel, herring, halibut, mackerel, mullet, butterfish, and lake trout, have a more moist quality than those which are without fat, such as cod. Therefore, as it is difficult to cook fish that is lacking in fat and keep it from becoming dry, a fat fish makes a more palatable food than a lean fish. The fat of fish is very strongly flavored; consequently, any that cooks out of fish in its preparation is not suitable for use in the cooking of other foods.

CARBOHYDRATE IN FISH.--Like meat, fish does not contain carbohydrate in any appreciable quantity. In fact, the small amount that is found in the tissue, and that compares to the glycogen found in animal tissues, is not present in sufficient quantities to merit consideration.

MINERAL MATTER IN FISH.--In fish, mineral matter is quite as prevalent as in meat. Through a notion that fish contains large proportions of phosphorus, and because this mineral is also present in the brain, the idea that fish is a brain food has become widespread. It has been determined, however, that this belief has no foundation.