92 Bulletin American Museum of Natural History [Vol. LIT 
adult flukes, about one-half inch long, live in the abdominal veins, 
especially in the portal vein and its branches. The eggs are character- 
isticaly oval, with a stout, terminal spine by means of which they pene- 
trate the wall of the bladder, being then voided with the urine; more 
rarely they invade the intestine and are eliminated with the feeces. While 
gaining their exit from the body, these eggs erode the mucous membrane, 
causing a certain amount of bleeding, which, mixed with the urine, 
produces the symptom known as ‘“‘parasitic hematuria.” Leiper (1915- 
1918) has worked out the life-history of this parasite. Upon reaching 
the water, the eggs hatch ciliated embryos or miracidia which enter the 
body of aquatic snails of the subfamily Bulinine. In Egypt the usual » 
host is Bulnus contortus (Michaud), although Leiper incriminates also B. _ 
dybowskii Fischer and B. innesz (Pallary).! Within the body of the snail, 
the miracidia develop into sporocysts, from which daughter sporocysts 
bud off. These migrate to the liver of the snail where they may become 
so numerous that the infection can easily be detected with the naked eye. 
Such infected snails later discharge through the pulmonary orifice every 
day for weeks free-swimming cercari# with a characteristically forked 
tail. The cercariz swarm on the surface of the water and die within 
forty-eight hours unless they are able to reach the body of their next, 
vertebrate host. They may enter a human being either by the mouth 
through the mucous membranes, or through the sound skin, and then 
migrate through the body to the abdominal veins. In South Africa the 
usual intermediate host is Physopsis africana Krauss, as first shown by 
Becker.’ Annie Porter? also found the cercarie in Lymnza natalensis 
(Krauss), but this is probably not of frequent occurrence. The probable 
source of an outbreak of bilharziosis in Portugal was traced by C. 
Franga* and by A. Bettencourt and J. Borges® to Planorbis dufourii 
Graells (=P. metidgensis Forbes; P. corneus var. metidjensis Bourguig- 
nat), since it was shown that this snail attracts the miracidia of S. 
1Leiper, R.T. 1915-1918. ‘Report on the results of the Bilharzia Mission in Egypt.’ Journ. Roy 
Army Med. Corps, XXV, 1915, pp. 1-55, 147-192, and 253-267, 3 Pls.; X XVII, 1916, pp. 171-190; 
XXX, 1918, pp. 235-260. 
*Becker, 1916, Med. Journ. South Africa, XI, p. 156 and XII, p. 42. F. G. Cawston, 1918, ‘Bil- 
harziasis in Natal.’ Parasitology, XI, pp. 83-93; 1922, ‘The experimental infestation of fresh-water 
snails, with special reference to the Bilharzia parasite.’ South African Jl. of Sci., XVIII, pp. 896-399. 
In Nyasaland the intermediate host is, according to W. H. Dye’s experiments, a species of Physopsis 
allied to globosa (Morelet) (See J. B. Christopherson, 1923, Nature, CXII, p. 436). In Sierra Leone 
Blacklock and Thompson (1924) infected experimentally a Physopsis (related to globosa Morelet) 
with S. hematobium. See also Ingram, A. 1924. ‘Note on a possible intermediate host of Schistosoma 
haematobium, in the Gold Coast.’ Ann. Trop. Med. Paras., XVIII, pp. 265-266. 
_'Porter, Annie. 1920. ‘The experimental determination of the vertebrate hosts of some South 
African cercariz from the molluscs Physopsis africana and Limnea natalensis.’ Med. Journ. South 
Africa, XV, pp. 128-133. An echinostome (Echinostomum xenopt) was found in both P. africana and L. 
natalensis and successfully reared in a frog of the genue Xenopus. A monostome has also been reared 
in Xenopus from cercarie in P. africana. 
41922, Bull. Soc. Path. Exot. Paris, XV, pp. 805-809. 
61922, Arq. Inst. Bact. Camera Pestana, V, pp. 133-135 and 189-230, Pls. vir—x11. 
