The danger of contact infection from such gross discharges as the sputum are sufficiently obvious. Material of quite as dangerous a nature is thrown out from the mouth as a fine spray in coughing, sneezing or loud speaking. Furthermore, it is a sad fact that cleanliness in a bacteriological sense is a very rare thing and the hands are usually more or less soiled with discharges from the nose and throat and too often from the intestines as well. Dr. C. V. Chapin, in his classic book, on "The Sources and Modes of Infection," has some striking paragraphs which, though not pleasant reading, must be pondered by all who would really understand how communicable disease is spread.
Probably the chief vehicle for the conveyance of nasal and oral secretions from one to another is the fingers. If one takes the trouble to watch for a short time his neighbors, or even himself, unless he has been particularly trained in such matters, he will be surprised to note the number of times that the fingers go to the mouth and the nose. Not only is the saliva made use of for a great variety of purposes, and numberless articles are for one reason or another placed in the mouth, but for no reason whatever, and all unconsciously, the fingers are with great frequency raised to the lips or the nose. Who can doubt that if the salivary glands secreted indigo the fingers would continually be stained a deep blue, and who can doubt that if the nasal and oral secretions contain the germs of disease these germs will be almost as constantly found upon the fingers? All successful commerce is reciprocal, and in this universal trade in human saliva the fingers not only bring foreign secretions to the mouth of their owner, but there exchanging them for his own, distribute the latter to everything that the hand touches. This happens not once but scores and hundreds of times during the day's round of the individual. The cook spreads his saliva on the muffins and rolls, the waitress infects the glasses and spoons, the moistened fingers of the peddler arrange his fruit, the thumb of the milkman is in his measure, the reader moistens the pages of his book, the conductor his transfer tickets, the "lady" the fingers of her glove. Every one is busily engaged in this distribution of saliva, so that the end of each day finds this secretion freely distributed on the doors, window sills, furniture and playthings in the home, the straps of trolley cars, the rails and counter and desks of shops and public buildings, and indeed upon everything that the hands of man touch. What avails it if the pathogens do die quickly? A fresh supply is furnished each day.
The control of contact transmission, the breaking of the chain of communication between the infected and the non-infected person, involves one or both of two measures. On the one hand, the spread of infective material from sick persons and carriers must be checked, so far as possible, and, on the other hand, the mouths of well persons must be guarded against infective material which, despite all our efforts, will to some extent be distributed in the world about us. The first half of this task involves the recognition of the sources of danger, and is of course greatly complicated by the presence of the unrecognized carriers. Much may be hoped, however, from the development of what may be called the sanitary conscience, the recognition on the part of each man, woman and child of the grave responsibility which he may incur by
