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this class are found in the infected areas and elsewhere, since infected people may move away from the sand districts. (2) Medium cases, including those in which the disease has

[graphic]

FIG. 42. A severe case of hookworm disease observed in Florida. Note the bloated face, the drooping shoulders, the prominent abdomen, and the thin arms and legs. The girl is about fifteen years old. Original, from a kodak photograph.

progressed to such an extent that a more or less anæmic condition is noticed, but other symptoms are not especially marked. If these patients were found outside the infected area, the diagnostician (especially if he is not familiar with the disease) would probably

not see anything particularly characteristic in them; many of these cases, however, show a more or less typical history, and if a history of residence upon sandy soil in tropical or subtropical regions can be obtained, uncinariasis should certainly be strongly suspected. If these cases occur in a family which also presents severe cases of uncinariasis, the diagnosis of hookworm disease in the medium cases is usually quite safe, even if a microscopic examination is not undertaken.

(3) Severe cases, in which we find that striking set of symptoms which even the laity in our Southern States attributes to "dirteating." These patients present a facies which is well recognized by Southern physicians. If the patient is found in a Southern sand area, the diagnosis is practically certain. If found outside of the infected area, with a history of previous residence in a Southern sand district, its recognition symptomatically ought not to be attended with difficulty. In case of doubt, if a microscope is at hand, the test may be made in less than five minutes; if no microscope is at hand, the blotting paper test (see p. 403) will usually suffice.

Turning now to an analysis of symptoms, I will give my observations on the severe cases. It is needless to state that the symptoms discused may vary in intensity, and that not every symptom mentioned is found in every severe case. We find on the contrary an imperceptible gradation between the severest and the lightest cases.

GENERAL PREDISPOSING FACTORS.-INFECTION OCCURS CHIEFLY ON SANDY SOIL.

In connection with the clinical history, the residence on sandy soil is undoubtedly one of the most important points to be obtained. If an anæmic patient gives no history of temporary or permanent residence on a sandy soil, uncinariasis is not absolutely excluded, but according to my experience the chances are against it. If, on the other hand, a history of sojourn or residence in a sandy rural district is obtained, the probabilities of uncinariasis are decidedly increased.

Nearly every case of the disease found during my recent trip was either living at the time in a sandy district or had lived in such a place a few years previously. As soon as I entered the sandy areas, uncinariasis was found. As soon as I left the sand, as at Albany, local foci of infection of uncinariasis disappeared.

Inquiry among physicians at first failed to elicit any definite statement regarding the soil on which anæmia was most frequent, but upon going farther south several physicians were met whose experience fully confirmed my observations on this point. One physician in particular, Dr. A. M. Burt, of Macon, was of the emphatic opinion that in bringing the condition which I have interpreted as uncinariasis into connection with the sandy soil, I had found the keynote to the distribution of the entire disease. Dr. McHatton, of Macon, called my attention to the fact that in antebellum days the slave owners in the Lower Mississippi Valley frequently provided special quarters, which were removed from the sand districts, and to which they sent the dirt-eating and other sick negroes and also negresses about to be confined, the view being held that a clay soil was more salubrious than a sandy soil. This view, in fact, I found to be rather prevalent among the farm hands. Time after time they remarked, "We were never sick so long as we lived in a clay district," "This disease developed after we moved upon sand," etc.

This view that uncinariasis follows the sand is supported by evidence obtained in Alaska by Mr. F. A. Lucas. After the discovery was made that uncinariasis, caused by Uncinaria Lucasi, was prevalent among the seal pups, Lucas showed that it was practically only the seals on the sandy rookeries which were infested with the parasites.

As stated elsewhere, I have also observed two outbreaks of uncinariasis among sheep and goats, caused by Uncinaria trigonocephala (Rudolphi, 1809) Railliet, 1900, on more or less sandy soil, and have further confirmatory facts in connection with one outbreak of the disease among dogs. Since returning from my trip I have found at least one reference in literature on uncinariasis

and ground itch to the effect that the soil in districts where certain cases have occurred was more or less sandy (see p. 376), but I have not yet found that any author lays stress upon this point.

In view of all the data at hand, I have no hesitation in expressing the opinion that uncinariasis, caused by Uncinaria americana, is pre-eminently a disease of sandy localities and, while infection elsewhere is not excluded, it is my experience that cases found in clay or rocky areas can usually be traced to a former visit or residence in a sandy place.

Just why this disease should follow the sand rather than the clay is not absolutely clear. Three explanations have occurred to me as working hypotheses which, though not absolutely satisfactory as final, will, I believe, explain part of the mystery.

1. We know that uncinariasis is spread through the feces; we know further that when the embryos hatch from the eggs they leave the feces and enter the surrounding water or moist earth, while there is no satisfactory evidence to show that they are blown around in the air in a dry state. (See Stiles, 1902b, p. 199.) Now, assume that a person walks over infected ground; if that ground is clay, he does not disturb the embryos which have crawled beneath the surface, except in wet places; if, on the other hand, the ground is sand, he not only stirs it up while walking, thus bringing the young worms nearer the surface again and thereby increasing their chances of producing an infection, but he is also likely to carry away particles of sand, together with embryos, with him on his shoes or feet, thus increasing his chances of becoming infected. It is further clear that children playing in sand will stir up more embryos than when playing on a clay soil, and will thus increase their chances of infection.

2. An additional explanation is that water will not pass through clay as it will through sand; hence on clay soil the embryos stand a greater chance of perishing or of being washed by rain into the streams. On sand, however, the embryos might perhaps work their

way through the soil* with the water, and thus infect surface wells. In advancing this hypothesis, I am not unmindful of the view, supported by excellent observers, that, since the embryos sink in water, drinking water is not necessarily a common source of infection. Granted that they do sink in water, a water bucket in a well also sinks, and the water from surface wells frequently contains sand particles that are heavier and larger than Uncinaria larvæ; hence we can not altogether ignore the drinking water as a possible source of infection. If, on the other hand, drinking water were the only source of infection, it is probable that in families where uncinariasis exists the intensity of the disease would show a greater tendency to uniformity.

Giles has examined fifty-six specimens of water from wells and ponds of villages affected with hookworm disease and sixteen of these he found by chemical and microscopical examination to be "bad" or "very bad." Yet on only one occasion did he find a rhabdite of doubtful origin in water. (Sandwith, 1894, p. 9.)

3. Oxygen is necessary to the development of the embryos and larvæ, and it does not seem unreasonable to assume that sand would on that account present more favorable conditions for the growth to the "encysted" stage, and probably also a longer preservation of that stage.

In this connection it may be noted that Looss has used charcoal as a medium in which to cultivate the larvæ of Agchylostoma duodenale.

*In an article which has just appeared, Looss (1903, p. 331) says:

"Further, during the six years of my residence in Cairo [Egypt], I have not heard, up to the present time, of a single case [of hookworm disease] in an European (my own case, of course, excepted). This fact speaks all the less [so much the less] in favor of the assumption of a more common dissemination [i. e., infection] of the disease through the drinking water, vegetables, etc., since [as] the mature hookworm larvæ, as experiments have shown, pass through the ordinary sand filter with surprising rapidity, and this even when the water is allowed, not to run off, but to stand." [Italics not in the original German.]

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