find a suitable medium to propagate, and where they may or may not be in position to get into the proper portion of the human animal. Almost any sort of insect may be a carrier, although there are some few peculiarly adapted for the purpose, and such a carrier may be the transmitting agent for a variety of diseases: it is not itself affected by any, and is in no sense a fellow sufferer.
It is different in the case of intermediate hosts; here the insect itself harbors one stage of the morbific organism and is itself a sufferer from one form of the disease. Its power of transmission is strictly limited and is restricted to one disease alone.
The best known and most abundant of the germ carriers is the common house-fly more recently called "typhoid fly." Now it undoubtedly
is a typhoid fly, but it is only one of several species that may be equally effective, and it is by no means a carrier of typhoid germs only. Its habits are such that it may be a transmitting agent for any intestinal disease and for many of the pulmonary and bronchial troubles as well. In a typhus or cholera epidemic it is a "cholera" or "typhus fly" and to call it the "typhoid fly" gives an unfounded suggestion of definite relationship between disease and insect.
But it certainly is marvelously well adapted as a carrying agent. Its omnivorous feeding habits, its persistence in seeking entrance at places where savory or other pungent odors attract it, and its foot and mouth structure make a combination difficult to equal. The pulvilli of the feet with their numerous minute hooked hairs are ideal collectors of microorganisms, and the lobed, lip-like mouth structure, with its array of pseudo-trachea for surface scraping, can hardly be surpassed in effectiveness. No doubt the house-fly is a danger of the first order, and there is no economic problem now before the sanitarian, of more importance than the elimination of this pest. That it can be done there is no doubt, and that in time it will be clone is equally certain.
