CLIMA TOLOGY 



t865 



in Bahia and Northern Brazil. It will thus be seen that the 

 recognition of the disease is becoming generally accepted, although 

 this was by no means the case when this chapter was first written. 



Climatology. — As far as is known at present, the disease exists in 

 Egypt, Central Africa, Uganda, South Africa, the Belgian Congo, 

 Central, South, and North America, and the West Indies. In 

 Brazil it is confined to the northern districts, being unknown in the 

 South. In Venezuela it is common around Caracas, where its 

 intermediate host is believed to be Planorhis guadelupensis Sowerby 

 by Iturbe and Gonzalez. 



-/Etiology . — The cause of the disease is Schistosoma mansoni. The 

 description and Ufe-history of the parasite is given in Chapter XXIV., 



mansoni. 



(Photomicrograph.) Fig. 768c. — Planovbis boissyi. 



Pathology. — The worms live in the portal vein, but are especially 

 attracted to the bowels, in the capillaries of which they lay their 

 eggs, which burst those vessels, and escape into the mucosa, causing 

 therein a dense cellular infiltration which leads to a thickening of 

 the coats of the bowel, and to the formation of papillomata, which 

 may become detached and form ulcers. Dense fibrous infiltration 

 of the peritoneum may also occur, and contain both eggs and 

 worms. The mucosa of the bowel is protected by a quantity of 

 mucus. In the rectum the mucus membrane is apt to become 

 hypertrophied, and to grow, forming large polypoid masses, or 

 adenomata, which may protrude through the anus. The ova may 

 affect the subcutaneous tissue of the sacral and coccygeal regions, 



