The animal parasites are destroyed by moderate degrees of heat, 60° C. or even less. Drying, salting, smoking, etc., cannot be relied upon to kill the larval parasites of meat and they may survive rare cooking. The comparative harmlessness of the beef tapeworm makes it not imperative to cook beef thoroughly, although the practice of serving raw scraped beef and very rare steak and roast beef to invalids is contraindicated by the possible danger of tuberculosis. On account of the frequency of trichinosis, rather than of measles, (cysticercal stage of taenia solium), pork should always be thoroughly cooked.

Very brief exposure of food stuffs to heat kills the great majority of vegetable germs and exposure of tuberculous meats and milk to a temperature of 100° C. or even a little less, kills most of the bacilli in a few minutes, though some of the bacilli with spores will survive. The contraindications to sterilization and even Pasteurization of milk and the choice between these methods, will l>e discussed more fully under the consideration of infant feeding.

Infants and young children are particularly prone to tul>er-culous infection from foods, or perhaps it would be more correct to state that the more susceptible individuals are infected early in life by reason of their greater exposure to possible sources of infection, largely in milk, of which adults drink comparatively little. On the whole, the best prophylactic measure is the inspection and destruction of tuberculous cattle and, fortunately, the milk is not usually contaminated with bacilli early in the disease, when its detection would be difficult.

For oeconomic reasons which are not imperative in America the sale of previously thoroughly cooked tuberculous meat is allowed in certain European countries and while probably toxins exist in the meat in small quantities, no practical danger seems to exist from the use of such meat and it is even possible that some degree of immunity is conferred by it.

Tetanus bacilli are among the most resistant germs known and they can be eliminated with certainty only by subjection to a boiling temperature for a period of nearly an hour. While infection with tetanus by ingestion is rare, it does occur. Moreover gelatin is frequently used as a haemostatic by injection, so that thorough boiling is necessary to insure against this disease. Mucilaginous vegetable substitutes for gelatin may be used in diet, but their nutritive value is doubtful.

Chemic destruction of parasites in food stuffs is not feasible although the customary and allowable methods of preventing the development of bacteria of decomposition diminish disease germs and grosser parasites, to some degree.

The prevention of infection by water may be summed up as follows: 1. Secure a supply free from drainage from cess pools, sewers, etc. This is practicable on a large scale only by a considerable extension of the powers of government. For small supplies, slow filtration through even a few yards of sandy soil, into a well, will remove even gross contamination with typhoid bacilli but if there is anything approaching a subterranean stream, as over a bed of rock or through a seam of rock or coarse gravel, infectious matter may be carried a long distance. There is no rule as to the distance or time required for spontaneous purification of running water. In a large lake, with ample opportunities for sedimentation, action of saprophytes, oxidation, etc., and with no appreciable current, the diffusion of infectious matter will not extend over more than a few miles.

2. Municipalities and institutions, having a relatively clear but infected water supply, can render it practically innocuous by slow sand filtration.

3. Large water supplies containing much clay are best treated by precipitation and so-called mechanic filtration.

4. Domestic and analogous disinfection of water is best effected by boiling.

5. For soldiers and travelers, when portable apparatus for boiling is not available, water may be quite certainly disinfected by standing for a few hours in a copper vessel or in a glass vessel to which hydrochloric acid is added in the proportion of 1:50(). The acid may be neutralized before drinking, by adding a little sodium bicarbonate.