Page:Popular Science Monthly Volume 52.djvu/305



N a recent address before a medical audience I defined the term "infectious" as follows:

"It is hardly necessary to say that by 'infectious diseases' we mean those diseases which result from the introduction into the body of some disease-producing agent. And I think we are justified in saying that an essential condition of infection is that the disease producing agent shall be capable of reproduction in the body of the infected individual—in other words, that it is a living organism. It matters not whether this living organism is large or small; whether it belongs to the animal or vegetable kingdom; whether it is located in the skin as in scabies, in the muscles as in trichinosis, in the lymphatics as in erysipelas, in the solid viscera as in amoebic abscess of the liver, in the intestine as in cholera, or in the blood as in relapsing fever, the introduction and multiplication of the living infectious agent constitutes infection."

The terms contagious and infectious are not synonymous. A disease is contagious when it is transmitted from the sick to the well by personal communication or contact, more or less intimate; and all contagious diseases are infectious—i. e., they are due to the introduction into the body of a susceptible individual of a living germ. But all infectious diseases are not contagious. Thus smallpox, scarlet fever, measles, diphtheria, influenza, etc., are infectious diseases