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Ash constituents of oysters. The fact that the oyster secretes such a large amount of calcium in its shell suggests that the edible portion may be relatively rich in calcium as compared with other flesh foods, which, as we have seen, are strikingly poor in this element.
According to Albu and Neuberg the edible portion of the oyster is strikingly rich in calcium, but an analysis in the writer's laboratory yielded :
This analysis shows a calcium content somewhat above that of meat but much below that of milk, and a preponderance of acid-forming elements as great as that found in lean meats.
Comparison of Poultry, Fish, and Shellfish with Other Flesh
Foods Attention has been called to the similarity of all these flesh foods and to the fact that the differences in general composition are chiefly attributable to varying fat content.
That there is also a general similarity in the structure of the proteins of shellfish, fish, and fowl and of ordinary meat protein such as beef is shown by the following table based on the work of Osborne:
TABLE 32. PERCENTAGES OF AMINO ACIDS FROM THE FLESH OF WIDELY
0.79 10.33 3.17 3.04
Glycine · · · · ·
Summation . .
2.28 4.90 3.47 14.88 1.95 7.38 2.02 5.77
4.74 3.53 3.21 16.48 2.16 6.50 2.47 7.24
5.82 3.15 4.51 15.49 2.20 7.47 1.76 7.59
· The digestibility of poultry and fish has been studied quantitatively by Milner and by Holmes in experiments in which the total percentages of net absorption from the digestive tract (coefficients of digestibility) were determined for protein and fat with the following results:
TABLE 33. DIGESTIBILITY OF POULTRY AND FISH.
(MILNER AND HOLMES)
The digestibility as thus determined is seen to be approximately equal to that of meats and appreciably higher than that of average mixed diet.
While these coefficients represent digestibility in the only sense in which it can be measured quantitatively, it is well known that the term digestibility is also used to indicate the relative ease and comfort with which foods are digested and the readiness with which gastric digestion is completed as evidenced by the time elapsing between the eating of the food and its entire passage from the stomach into the intestine. In these respects oysters, lean fish, and chicken are held to be even more digestible than lean beef, while fat fish, duck, goose, lobsters, and crabs are held to be of about the same order of digestibility with ham and pork. (See, for instance, the Table of Comparative Digestibility in Gilman Thompson's Practical Dietetics.)
Place in the diet. From most standpoints poultry, fish, and shellfish may be regarded as interchangeable with the ordinary meats. As in the case of meats, their chief nutritional significance is as sources of protein. Drummond has found fish proteins to resemble meat proteins in efficiency for the support of
growth. Furthermore poultry, game, fish, and shellfish all show about the same mineral deficiencies as do the meats and grains. There are some indications that fish have a better vitamin A content than ordinary meats.
The comparative economy of these different types of flesh food varies widely with locality and season. While game has become so scarce and costly as to be no longer an important factor in the food supply, the prices of poultry, fish, and shellfish appear at present to be rising less rapidly on the whole than the price of beef. The breaking up of the great cattle ranges into small cultivated farms naturally tends toward a relative (perhaps not absolute) decrease in beef production and an increase (both absolute and relative) in poultry culture. Oyster culture is becoming systematized so that, while oysters will doubtless remain an expensive food, the supply will probably increase. The fishery industries are also capable of great development both by improved methods of handling the species now regarded as important and by utilizing as food the flesh of species which in the past have been neglected. Thus it is said that a few years ago sturgeon was so little prized as food that much of it was used as fertilizer, while now smoked sturgeon is in good demand; and that still more recently the garfish, formerly regarded merely as a pest, has begun to find a market as a food fish.
Since in the nature of the case the meat production of the country cannot be greatly increased except at the cost of a restricted output of other farm crops, we may anticipate a constantly increasing tendency towards better conservation and more economical utilization of the fishery products as food.
ATWATER. The Chemical Composition and Nutritive Values of Food Fishes
and Aquatic Invertebrates. Report of the United States Commission on Fish and Fisheries, 1888.
ATWATER and BRYANT. The Composition of American Food Materials.
United States Department of Agriculture, Office of Experiment Stations,
Bulletin 28 (Revised). KÖNIG. Die Menschlichen Nahrungs- und Genussmitteln. LANGWORTHY. Fish as Food. United States Department of Agriculture,
Farmers' Bulletin 85 (Revised). Prescott and WINSLOW. Elements of Water Bacteriology, Chapter XII. THOMPSON. Practical Dietetics. TRESSLER. Marine Products of Commerce. United States Bureau of Fisheries. Reports and Bulletins. WILEY. Foods and Their Adulteration.
Poultry and Game MILNER. Experiments on the Digestibility of Fish and Poultry. Storrs
(Conn.) Agricultural Experiment Station, Seventeenth Annual Report,
pages 116-142 (1905). WILEY, et al. A Preliminary Study of the Effect of Cold Storage on Eggs,
Quail, and Chickens. United States Department of Agriculture, Bureau
of Chemistry, Bulletin 115 (1908). PENNINGTON. Studies of Poultry from the Farm to the Consumer. United
States Department of Agriculture, Bureau of Chemistry, Circular 64
(1910). HOUGHTON. Effect of Low Temperatures on Ground Chicken Meat. Jour
nal of Industrial and Engineering Chemistry, Vol. 3, pages 497-506
(1911). OLDYS. Game Market of To-day. United States Department of Agricul
ture, Yearbook for 1910, pages 243–254 (1911). PENNINGTON and HEPBURN. The Occurrence and Permanence of Lipase
in the Fat of the Common Fowl (Gallus domesticus). United States
Department of Agriculture, Bureau of Chemistry, Circular 75 (1911). PENNINGTON, WITMER, and PIERCE. The Comparative Rate of Decom position
of Drawn and Undrawn Market Poultry. United States Department
of Agriculture, Bureau of Chemistry, Circular 70 (1911). PENNINGTON and HEPBURN. Studies on Chicken Fat. Journal of the
American Chemical Society, Vol. 34, pages 210-222 (1912).
Conservation of Poultry and Eggs. American Journal of Public Health,