It is well known that influenza is an infectious disease, which rapidly spreads through the family and the community, but it is not so well known that the so-called “common colds,” ordinary sore throat, and tonsillitis are also highly contagious. The infection is carried from one person to another by direct contagion; the air is being constantly sprayed with the germs of disease in talking, laughing, sneezing, and coughing. In coughing and sneezing it is not sufficient to hold the hand before the mouth—a handkerchief must be used for this purpose. _Colds_ are among the most frequent of the so-called minor ailments in this country. The causes are the overheating of the houses, the great dryness of the air, badly ventilated houses and public assembly rooms, which render people very susceptible to the great variations in temperature. _Prophylaxis_, or _the prevention of colds_, combine all those measures which promote the general tone of the system, and may be said to embrace all the elements of personal hygiene. Good digestion and proper nourishment of the body with suitable food; the proper ventilation of houses, all public buildings and conveyances, for in these latter the public are brought into very close contact with their fellow-men. Local prophylaxis would consist in the toilet of the nose and throat—the removing of adenoids and enlarged tonsils. The individual must remember that she can reinfect herself; for this reason, an abundant supply of handkerchiefs must be used; they should be placed in a handkerchief bag and washed separately. Packs of cards should be thrown away before they become soiled. Sprays and atomizers must be individual property, and be kept thoroughly cleansed. With the exception of deep-seated chest colds, in the early stages a cold may often be nipped in the bud by a few hours of hard sudorific work in the open air. In half a day the nasal ducts and respiratory system will throw off irritating matter that would take much longer time if the patient remained indoors and relied on the action of drugs alone. _Treatment._—Other methods of treatment are a hot tub-bath on retiring, an active but not too severe cathartic, as two grains of calomel, taken just before going to bed, and, if the individual is chilly, a hot lemonade should be taken at the same time. Both the cathartic and the free perspiration will aid in relieving the internal congestion and thus aid in its abortion. A cold sponge should be taken the following morning to tone up the system. Turkish baths are also useful in breaking up colds; again, the precaution must be taken to avoid chilling on leaving the bath.