While water and milk are doubtless the most important food materials in their relation to disease, other foods should be considered in this connection. These include meats, raw oysters, milk products, fruits, vegetables, and certain commercially prepared foods, indeed, any material which is subject to injurious fermentation or to contamination in preparation and through handling in the market. It may be said in a general way that the causes of unhealth-fulness in these foods may arise from two general causes, viz. (1) the acquisition of disease-producing forms of life from without, and (2) the development within of disease organisms or of toxic bodies through fermentative processes. Certain of these disease-producing conditions rarely occur. The danger from them is slight as experience shows, and all such dangers may usually be avoided by intelligent precautions.

The disease organisms that may be found in the tissues of animals used for food are trichina and the germs of tuberculosis.

320. Trichinosis

Since 1860 it has been known that the muscular tissue of swine is sometimes infested, though perhaps rarely now, with a minute parasitic worm known as the Trichina spiralis. It is parasitic on other domestic animals, particularly cats, rabbits, rats, and mice. The young worms', after developing from the eggs, become imbedded by millions in the muscles of the hog, and are then invisible to the naked eye. After a time, they become encysted, and at the end of a year or so are visible to the naked eye as specks scattered through the muscular tissue or red meat. In this form, the worms are dormant, and may live a long time. When uncooked pork so infested is eaten by man, the worms are liberated, attach themselves to the lining of the stomach, and the females produce broods, sometimes of as many as a thousand young worms. These young find their way into the tissues of the intestines, and finally throughout the whole system. It seems that with the rarity of this disease in swine, and with present methods of inspection, pork infested in this way very seldom finds its way into the family larder. In any case, the thorough cooking of pork renders it a safe. food.

321. Tuberculosis

The widespread existence of this disease not only among dairy cows, but among animals slaughtered for meat, even those raised and fed on the western plains, has rendered the public solicitous concerning the healthfulness of beef, so much of which is eaten without thorough cooking. There is a not unnatural prejudice against eating the flesh of an animal known to have been affected with tuberculosis; and in dealing with this disease in the way of suppression, animals so affected have quite generally been killed and buried. The indiscriminate rejection of such animals for human consumption has undoubtedly caused the waste of a large amount of perfectly safe food material. Experience has shown that the flesh of animals that are affected with tuberculosis within certain limits may be safely used as food for man. This is so because of the nature of the disease. Its effect, at first at least, is not to diffuse diseased, toxic or infectious material throughout the entire mass of the animal's body, but to destroy the tissue of certain glands or organs in which it gains a foothold. The regulations of the federal meat inspection that have been established in the large abattoirs permit the carcasses of animals to be sold as sound when the lesions (diseased tissues) are localized and are restricted to certain organs, and exist in the less dangerous forms. It is not true, then, that the flesh of all tuberculous animals is unfit for human food, or that such meat is wholly excluded from the market, even under the most rigid inspection. There is good reason for maintaining inspection, and consumers have a right to demand that this be of the most thorough kind.