Prevention and Eradication 



51 



(3) The co-operation of the natives in Egypt could only follow 

 upon years of instruction resulting in a radical change in the habits 

 of the people. 



The remedy is to be sought elsewhere. Fortunately, there are 

 certain physical conditions almost peculiar to Egypt which are 

 inimical to the cercaria and its carrier, and which, if properly 

 exploited, might bring about almost complete eradication of the 

 disease in the course of a few years. 



Water is absolutely essential for the life of the Bilharzia outside 

 the body. In Egypt all water is derived from the Nile, directly by 

 irrigation canals or indirectly by seepage into wells, and from rain. 



Fig. 23. — Showing annual rise in the Nile during the autumn. 



The Nile : 

 Irrigation. 



Almost the whole of the water required for the 

 cultivation of the land and for the use of the 

 population is derived from the Nile. Until 1820 

 the cultivated land was irrigated by the Nile only during its 

 annual rise. The land at the river's edge is ordinarily about nine 

 metres above the river-bed. Every autumn the river rises from 

 seven and a half to ten metres above its bed, as shown in the 

 accompanying diagram (fig. 23). In the early days of Egyptian 



