On the whole, the evidence is conclusive that typhoid germs not only may be accidentally carried on the bodies of house-flies but may pass through their bodies and be scattered in a viable condition in the feces of the fly for at least two days after feeding. Similar, results have been reached in experiments with cholera, tuberculosis and yaws, the last-mentioned being a spirochæte disease. Darling (1913) has shown that murrina, a trypanosome disease of horses and mules in the Canal zone is transmitted by house-flies which feed upon excoriated patches of diseased animals and then pass to cuts and galls of healthy animals. Since it is clear that flies are abundantly able to disseminate viable pathogenic bacteria, it is important to consider whether they have access to such organisms in nature. A consideration of the method of spread of typhoid will serve to illustrate the way in which flies may play an important rôle. Typhoid fever is a specific disease caused by _Bacillus typhosus_, and by it alone. The causative organism is to be found in the excrement and urine of patients suffering from the disease. More than that, it is often present in the dejecta for days, weeks, or even months and years, after the individual has recovered from the disease. Individuals so infested are known as "typhoid carriers" and they, together with those suffering from mild cases, or "walking typhoid," are a constant menace to the health of the community in which they are found. Human excrement is greedily visited by flies, both for feeding and for ovipositing. The discharges of typhoid patients, or of chronic "carriers," when passed in the open, in box privies, or camp latrines, or the like, serve to contaminate myriads of the insects which may then spread the germ to human food and drink. Other intestinal diseases may be similarly spread. There is abundant epidæmiological evidence that infantile diarrhœa, dysentery, and cholera may be so spread. Stiles and Keister (1913) have shown that spores of _Lamblia intestinalis_, a flagellate protozoan living in the human intestine, may be carried by house-flies. Though this species is not normally pathogenic, one or more species of _Entamœba_ are the cause of a type of a highly fatal tropical dysentery. Concerning it, and another protozoan parasite of man, they say, "If flies can carry _Lamblia_ spores measuring 10 to 7µ, and bacteria that are much smaller, and particles of lime that are much larger, there is no ground to assume that flies may not carry _Entamœba_ and _Trichomonas_ spores." Tuberculosis is one of the diseases which it is quite conceivable may be carried occasionally. The sputum of tubercular patients is very attractive to flies, and various workers, notably Graham-Smith, have found that _Musca domestica_ may distribute the bacillus for several days after feeding on infected material.