. Public health and preventive medicine. ity.—It is very high, though the disease may apparently abort. Incidence.—Age exercises no influence, nor does sex. Race.—Negroes are chiefly liable, but the disease is not confined tothem. Method of Transmission.—UnknoAvn. If due to F. perstans, probablyby means of drinking-water. Prevention of Origin and Spread.—A pure water supply. Otherwiseunsatisfactory, owing to doubtful etiology. F. lymphatica, F. volvulus, F. rest (for mis, and F. inermis are very rare inman. They are parasitic in the lower animals. F. demarquaii is a small filaria found in the
. Public health and preventive medicine. ity.—It is very high, though the disease may apparently abort. Incidence.—Age exercises no influence, nor does sex. Race.—Negroes are chiefly liable, but the disease is not confined tothem. Method of Transmission.—UnknoAvn. If due to F. perstans, probablyby means of drinking-water. Prevention of Origin and Spread.—A pure water supply. Otherwiseunsatisfactory, owing to doubtful etiology. F. lymphatica, F. volvulus, F. rest (for mis, and F. inermis are very rare inman. They are parasitic in the lower animals. F. demarquaii is a small filaria found in the blood of West Indian natives, 94 MEDICINE and present both by day and night. It may be the embryonic form of thenext variety. F. magelKcesi.—Has been once found post-mortem in South America. F. ozzardi is a name common to two South American varieties of embryo,one of which, in its parental form, is identical with the parental form ofF. perstans. Bilharzia haematobia male a distomum, but is not hermaphrodite. The. Pig. 34. —Bilharzia hcema- tobia, male ami female.(After Leuekart.) i- about | in. long, and is a white worm reallyflat in shape, but having its edges infolded so as topartially enclose the female in the groove so formed(Fig. 34). The female is of darker hue, about t , thread-like, and is thinner than the male worm,which encloses her in his canal, with the exception ofher head and tail ends. These parasites are found inthe blood of the larger veins, especially in the portalsystem, and the female, passing from these to smallveins in the rectal and bladder walls, there depositsher eggs. The oval eggs, which have translucentcapsules and are furnished with one spine apiece,penetrate the rectal or bladder wall, causing effusion ofblood, and are voided in the faeces or urine (Fig. 35,a and b). Each contains a ciliated embryo (Fig. 35, c)which escapes from the egg (Fig. 35, cl), and if itgains access to fresh water is capable of development,s
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