common among the children; it has not been unusual, for instance, to find that 50 to 100 per cent of the specimens of feces collected from the families contain the protozoa in question. To assume that the infections take place in this village by means of the water presupposes that these nonmotile spores travel through a layer of sand a distance of more than 100 feet to a driven well; this assumption does not seem justified. That the children might get their hands soiled with feces, directly or indirectly, from the privies, is conceivable; but this method of infection seems less probable than the fly method, since the children in this particular village rarely pass through the alley between the privies; that infection per hands might take place, as for instance, from soiled privy seats, is to be admitted. That cats, dogs, rats, and chickens might spread the fecal materialis to be admitted, but such admission would not weaken the idea of fly transmission. Turning now to the idea that flies play an important rôle as mechanical transmitters of these protozoa, the following points should be considered: 1 As already stated, flies breed and feed by the thousands in these surface privies, and they fly to the kitchens that are near by. For instance, in 24 hours' time 293 flies were caught in a Hodge fly trap placed in one of these privies, and 1,742 flies were caught during the same 24 hours in another fly trap placed in the corresponding kitchen, about 40 feet away. Further, flies were seen passing to and fro between the privies and the kitchens. With this constant exchange of flies between the feces in the privy and the food in the kitchen, the possibility is given of a daily smearing of the food with small particles of fecal material on the bodies or legs of the flies. The carriage of lime by flies from privies to food is too well known to call for discussion. Since the spores in question are smaller than the particles of lime, there seems no reason to doubt that these spores also are carried by the flies. The process seems so self-evident that a laboratory demonstration of the fly as an actual carrier may be viewed as almost superfluous. Nevertheless, experiments to demonstrate the point in question were made. Flies caught in the houses and in the privies were examined, but with negative result. When we considered the minute size of the spores (Entamoeba coli about 15 in diameter, Lamblia about 10 by 7p, Trichomonas with adults 4 to 15μ long by 3 to 4μ broad), these negative findings are not surprising. In order to obtain a number of flies that were known to have visited infected excreta a specimen of human feces containing a large 1 Stiles and Miller, The ability of fly larvæ to crawl through sand. Public Health Reports, vol. 26, No. 43, Aug. 25, 1911, p. 1277. number of Lamblia cysts was diluted with sterile water, stirred to an even consistency, sprinkled with a small amount of brown sugar (in order to attract additional flies), and used as bait in a Hodge fly trap, which was placed in a barn. The several hundred flies that were caught during 24 hours were etherized and transferred from the trap to a clean test tube containing some sterile water. After the tube was thoroughly shaken some of the water was centrifugalized for about 5 minutes. The sediment was then examined under an oilimmersion lens, and 6 Lamblia cysts were found. Thus it is demonstrated that the fly is capable of carrying the spores of Lamblia. If flies can carry Lamblia spores measuring 10 by 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 Entamaba and Trichomonas spores. Admitting the possibility of the transmission of these spores by various methods (flies, rats, dogs, hands, vegetables, water, etc.), whatever the method that occurs in any particular case, the presence of the protozoa in question means that the person showing the infection has been eating excreta; ergo, when a person harbors any one of these protozoa we have proof that there is something wrong with the sanitary conditions, either at or near the house where this person lives or has lived or elsewhere in some place influencing the life of said person. If there is a surface privy in the back yard of the house or of the house next door to where the infected person lives, this is the nearest place that comes into consideration, and although we have no proof that the particular infection found actually came from that particular privy we have a demonstration that he has actually swallowed excreta and that the conditions are favorable at his residence for a continuation of this diet as a daily routine. Turning now to practical experience in examining for these protozoa we have found the following infections in the examination of one series of 187 unselected persons: Thus those persons (chiefly children) living (chiefly in the city) at houses provided with a privy showed 30 per cent infection as against 20 per cent among persons (chiefly children) living at houses not provided with a privy but connected with the sewer; in all or practically all of the latter cases, however, privies were found in the same or in the adjoining block of houses; hence these people were still subject to the possibility of fly-borne infection, although the chances were slightly reduced. Taking all of the 187 persons together it is seen that 43 of them (23 per cent) had been eating excreta, apparently human excreta. Practical application of the test.-We are using this test in a practical way to induce people to improve the sanitation. Upon finding the infection present we notify the mother of the child that the microscopic examination shows that her child has swallowed excreta, probably in food contaminated by flies, from some surface privy; we advise her to request the local health officer to inspect the block in which she lives to determine whether there is any insanitary privy near her, supplying her table with contaminated flies, which might continue the infections to her child or to other members of the family. The mother sees some privy in a near-by backyard, sees-as she never saw before the danger of the surface privy, and she demands an improvement in the sanitation. Of all methods by which we have tried to arouse sentiment against the surface privy, we know of none equal to this in promptness of result. The possible exceptions to the fly transmission do not worry us. The water here is sand-filtered and can scarcely play an important rôle. Flies can and do carry the infections; we demonstrate the presence of the infection; the mother sees the privy and the flies, and she sees that the possibility of continued infection is ever present in this climate. In case of necessity we occasionally tell the family that we can not prove whether the infection came from the privy of a white family or of a negro family, and this statement tends to add to the desire to have the insanitary privies made sanitary. |