62 Bilharziasis 
on account of its cheapness, was being largely used by the natives for domestic, 
drinking, and other purposes. 
At the request of Dr Todd, the Director of the Public Health Laboratories, 
we inspected the storage reservoirs of this crude unfiltered water supply 
derived directly from the Nile. 
In the two main storage tanks Bullinus were found on the green water- 
weeds growing below the surface. In a small adjacent tank, 15 feet in diameter, 
250 Bullinus were collected in a few minutes from the inlet pipe that comes 
from the Nile. 
In the old disused filter beds near those at present in use, many thousands 
of shells of Bullinus, and some of Planorbis boissyi, were found. 
These findings suffice to explain the incidence of bilharziasis amongst the 
native children of Cairo who have not been outside the City itself, and prove 
the danger of this unfiltered water supply to the whole community. The 
molluscan fauna in the ponds and fountains of public gardens of Cairo are 
also derived from this water supply. We have frequently noted that either 
the spawn, the young, or the adult snails themselves can withstand the water- 
pressure in the piping. Thus at el Marg, infested snails may be obtained in 
quantity in the railway tanks which derive their water supply from adjacent 
canals. 
While the infectivity of the Nile water has never been demonstrated, our 
observations support those of Leiper on the subject. The presence of snails 
in the pipe conveying water from the Nile, and the large number of shells 
left in the mud on the banks when the water recedes, prove the wide distribu¬ 
tion of fresh-water snails in that river. Felucca men (boatmen) state that snails 
are to be found adherent to their boats if they have been anchored for any 
length of time during the summer months. Several years ago an outbreak 
of bilharziasis occurred amongst soldiers who had bathed in a specially con¬ 
structed floating wooden bath, in the Nile at Kasr-el-Nil bridge. Here the 
conditions for the concentrated action of cercariae were ideal, for snails 
adhering to the side of the fiamework nearest the current would create a zone 
of infectivity in the water immediately beyond. 
All along the Nile banks deposits of human faeces may be observed, 
similarly urinary contamination occurs, owing to the un-hygienic habits of the 
natives. 
Along the banks where the reeds and grasses cause the water to become 
stagnant, snails maybe observed, and it is here that the miracidia from infected 
excreta have every chance of finding their intermediary hosts. Native 
water-carriers fill goat skin bags with this water, and sell it to the native 
population at a very cheap rate. It is used by them for drinking and 
domestic purposes. This practice may constitute another very real danger to 
the community. 
