inclosed in a lacquered can, before the meat is processed. This precaution is taken to avoid the blackening of the flesh. Prawns are simply large shrimps, and are obtained along the Southern Atlantic coast early in the season before the smaller shrimp are plentiful. MISCELLANEOUS ANIMAL FOODS Turtles inhabiting both fresh and salt water, are important foods. The green turtle, which sometimes weighs several hundred pounds, is used chiefly in making soups which are greatly valued for their flavor. Turtle meat contains about 20 per cent. of protein and a small amount of fat. It is generally considered a luxury, and is rather indigestible. The flesh is cut into slices and sundried for preservation. The terrapin, a salt-marsh tortoise, is found along the North Atlantic coast. The diamond-back, and the red-bellied terrapin is in common use for edible purposes. The flesh is highly esteemed for its digestibility, and agreeable flavor. On account of the demand for terrapin, there is danger that it will be exterminated in the eastern United States, and it is already so expensive as to be classed as a luxury. The effort to raise terrapin artificially has not been wholly successful. Frogs, legs are a standard food in the markets of continental Europe at certain seasons of the year and are gradually being utilized in the United States. They are in the best condition in the autumn and winter. The flesh, which has an extremely delicate flavor, tastes somewhat like that of chicken, and is easily digested. CHAPTER XVI MILK AND DAIRY PRODUCTS Milk, since it contains all the substances necessary to sustain the life of the young animal, has always been regarded as an ideal food, and in addition to woman's milk, the natural food of infants, the milk of the cow, goat, ass, ewe, mare, camel and reindeer have been used from the earliest times as human food. The foods manufactured from milk, including butter, cheese in almost endless variety, koumiss and other fermented beverages, have also been used by different peoples from the remote ages of the past. Butter was used by the Hindus as early as 2000 B.C. both as food and in their religious ceremonies, and it is mentioned by the early Hebrew, Greek and Roman writers. It is however a product of the temperate zones rather than the torrid, as it melts so readily in warm weather. COW'S MILK Considering for the present cow's milk only, it is well known that the quality varies within wide limits dependent on the breed, age, condition, stage of lactation, and food of the animal, and the season of the year. If examined with the microscope, milk will be seen to contain numerous fat globules of a pearly luster, and about 0.005 millimeters in diameter. It is the presence of these globules that give to milk its yellow color, so that we are accustomed to judge something of the quality of the milk by its color. The "reaction" of human milk and that of herbivorous animals when freshly drawn is slightly alkaline, while that of carnivorous mammals is as a rule slightly acid. In the case of cow's milk the reaction may appear to be amphoteric, that is, it gives the acid or the alkaline reaction according as different indicators are used.1 The specific gravity of milk varies from 1.029 to 1.035 at 60° F. This is not considered as valuable an index of the quality of milk as formerly. It is practically impossible to obtain clean milk from cows that are kept in filthy surroundings. To obtain milk of excellent quality the cows should be housed in light, clean, warm, well-ven tilated stables. In the best dairy practice the floors are of concrete, the windows are screened to keep out flies, and an abundance of good water is supplied. The udder of the cow is carefully brushed and cleaned before milking. The attendants are free from infectious disease, wear clean clothes when milking, and avoid noise and confusion in handling the cows.2 The custom that has recently been adopted in the best dairies for marketing milk in closed bottles is an advance in sanitation. In Europe it is sold from tin or brass cans. (Fig. 76.) Milking machines are coming into general use for large dairies. 1 Bordas, Eighth Int. Cong. Ap. Chem., Vol. 18, p. 67. 2 U. S. Dept. of Agri. Bur. An. Ind. Circ., 142. As milk affords an ideal medium for the growth of bacteria, it is of importance that the milk room, where the milk is stored, be clean and cool. The milk should be cooled to below 50° F. as soon as possible after it is drawn, and kept cold until delivered to the customer. Tuberculous Milk The cows should be examined from time to time to determine whether they are afflicted with tuberculosis, and any suspected animal should be immediately isolated from the rest of the herd, and its milk rejected. Says Dr. F. H. Billings: "Tubercle bacilli in milk are generally of bovine origin. If a dairy cow is suffering with tuberculosis there is a chance of the milk becoming contaminated with the bovine type to which children are particularly susceptible. The bacilli find entrance through lesions in the udder and through particles of excrement that fall into the pail in the process of milking. It has been shown that cows afflicted with the disease may pass virulent bacilli with their feces, and it is probable that contamination from this source is of greater frequency than it is from diseased udders. Dependence on ordinary clinical symptoms for detecting tuberculosis in dairy herds should not be considered, as animals may give every appearance of being healthy and yet may be scattering virulent organisms. Reliance should be placed rather on the "tuberculin" test, and the removal from the herd of those animals which react with it." "The occurrence of bacilli of human origin in milk is sometimes traceable to careless handling by persons afflicted with consumption. Though this source of danger doubtless plays a less important rôle than the other, it is real, and great care should be exercised in excluding diseased persons from handling milk that is used by others." "While man is the main source of human infection (with tuberculosis), the proportion due to material of bovine origin is sufficiently large to make it very important that proper steps be taken to prevent this source of human disease. It must be conceded that while infected meat cannot be altogether excluded as a source of human tuberculosis, in nearly all the cases of human infection from bovine sources, the vehicle is milk or milk products."1 In many parts of the country, regular inspections of the dairies are made by competent veterinarians, under the direction of the state or the municipal health authorities. Abnormal Milk The secretion from the udders of cows and other mammals for some days after the birth of the young acts as a purgative and has a pungent taste. It is called "colostrum," and is not considered fit for human food. It contains less water and sugar than normal milk and much more albumin and ash. The amount of fat is extremely variable and it contains small organized bodies which are generally regarded as the débris of the cell structure of the gland. The milk secreted for some weeks before the calf is born is also usually rejected. Composition of Milk The composition of the milk of different animals is as follows:2 Cow's... Human. Ass's.... 1.0315 87.17 3.02 0.53 3.55 3.64 4.88 0.71 4.91 0.89 5.67 0.35 1.55 2.22 1.64 5.99 0.51 It is evident that milk, although a liquid, contains less water than some vegetables and fruits, for instance asparagus, which 1 Milk and the Public Health, Savage, p. 321. ? König. |