GO 
Bilharziasis 
In the birkets and canals large numbers of Planorbis boissyi are always 
to be found, and greatly out-number any other species of fresh-water snail. 
Bullinus, on the other hand, is not so common. On reference to Table IV 
it will be seen that from over 5000 dissections of these snails, 18 per cent, were 
infested with S. mansoni. On the other hand, in over 1000 dissections of 
Bullinus, only T9 per cent, were found to be infested with S. haematobium. 
In e] Marg at any rate it would seem that the occurrence of rectal bilharziasis 
in man ought to be much more common than that of urinary form. As a matter 
of fact both rectal and vesical forms are exceedingly frequent amongst the 
native population, though from its situation the former bilharziasis (S. man¬ 
soni) requires more painstaking observation for its detection. 
A glance at the map of Egypt will show that the bathing sites where troops 
acquired infection are widely spread over various stretches of fresh water, 
including those of both Lower and Upper Egypt. 
Thus, TeTeTKebir and Abou Soueir are on the Zag-a-zig to Ismalia canal; 
Serapeum is situated on the sweet-water canal between Kantara and Suez; 
Beirut and the Fayoum are both in Upper Egypt. 
They therefore serve, in a general way, as excellent indications of the poten¬ 
tialities of these particular spots. 
CONCLUSION. 
As a result of this study of the clinical types of bilharziasis originating 
in a given locality, and from subsequent investigation of the molluscan fauna 
of that area, we are presented with a remarkable corroboration of Leiper’s 
work. The specificity of these two species of snails for their respective parasites 
has, in this fashion, been repeatedly proved. 
It is surely very satisfactory to be able to substantiate that the distribution 
of the disease in man corroborates in such a remarkable way the experimental 
facts observed in the laboratory. 
Wherever the Planorbis is the predominant sptecies there will rectal bilharzi¬ 
asis be found, and wherever Bullinus abounds there the urinary form of the disease 
will be the most prevalent. 
The statistics given in Table VI show how heavily parts of the Delta 
district are infested with S. mansoni. From these statistical studies, from clini¬ 
cal observation, and from other data, we are firmly convinced that intestinal 
bilharziasis (S. mansoni) is much more prevalent amongst the Egyptian popu¬ 
lation of Lower Egypt than is at present recognized. 
Intestinal bilharziasis is more difficult to diagnose clinically for the follov - 
ing reasons: 
(1) Intestinal symptoms in man are frequently latent, and when present 
do not, in a tropical country, attract so much attention as do urinary ones. 
(2) Many more ova are produced by S. haematobium than by S. mansoni, 
and therefore the former are much more easily found under the microscope in 
routine examination of the discharges. 
