KEEPING WELL 425
Many of these germs are exceedingly tenacious of life; they may remain inactive a long time, even though they do not develop and grow. Some of them will live even in a medium which is without air, but the most of them, it is believed, require air like other forms of life. Some of them bear a temperature below the freezing point without discomfort and are often found in ice; none of them will endure a temperature above the boiling point for any length of time. Most of them will succumb to powerful chemicals like sulphur, chlorine, mercury, and formaline.
Food which is thoroughly baked or boiled is not a source of trouble from disease germs, but it does not interfere with the work of germs which are already in the alimentary canal, and their treatment can hardly be undertaken until they have manifested their presence by some disturbance in the individual affected. Raw food is always taken with risk; it may be disinfected with chemicals, but this is usually inconvenient. It may be thoroughly disinfected with heat—that is, by cooking. Water, which is boiled or distilled, is free from germs; also artificial ice, which is made from distilled water. Five or ten drops of dilute hydrochloric acid in a glass of water will sterilize it sufficiently, and the acidulous taste of the water will not be objectionable to most people.
Milk is so important an article of food and so often a source of disease from the bacteria which it contains, that a few words concerning its disinfection or sterilization are demanded. Prolonged boiling of milk destroys its germs, but it also coagulates its caseine, and makes it more difficult to digest. There are several excellent forms of apparatus on the market (Soxh-let, Seibert, and others) for sterilizing milk when used as food for infants, which may be adopted with safety.
Pasteurization of milk consists in subjecting it to heat from 15 8° to 1760 F. for half an hour or longer, and then rapidly cooling it to 540 F. or less. This will destroy, or render inactive, the bacteria which it may contain, but will not coagulate the caseine.
Those who, as nurses, doctors, or assistants, have attended the sick with the eruptive diseases—measles, scarlet fever,