179 
At post mortems, it is not uncommon to find males alone 
in the portal vein. These males are often conspicuously of the 
same size, in other words, all of the same age. They must have been 
generated at about the same time ; this would become comprehensible 
on the assumption that they are generated in one sporocyst. If 
one sporocyst may produce males I see no reason which forbids the 
assumption that the females take their origin in separate sporocysts. 
As females are. as a rule, found much more rarely than males, it may 
be admitted that male sporocysts are commoner than female. 
This is the way in which, according to the facts at present 
available lam forced to explain the arrival of the parasites m 
the human body. I will now describe how I seem to see the con¬ 
nection between the special aspects of the disease and the habits of 
the population as they are observable, in tlie first place, m Egypt. 
In Egypt, Billiarziosis is very common. In the towns it is especially 
the children who are infected ; among our students, there are always 
some who have, or have had, haematuria. ’ Some of them assert 
emphatically that they have got it while in the country. In all of 
them the disease lasts for some years and then disappears. A 
severe cases come from the country. T he Egyptian peasants 
usually work their fields in companies; sometimes of two or three, 
sometimes of several dozens; standing with their feet, and working 
with their hands, in the water or the mud. They often also bathe 
in companies in canals with slowly flowing water, pools, &c. One 
of them who is infected with urinary Bilharziosis, when urinating into 
the water, infects it with several hundreds, perhaps thousands, of 
eggs. In warm weather the iniracidia hatch within a few minutes. 
They have at once the opportunity of finding a new shelter, either 
in the skin of the man who voided the eggs or in the legs or hands 
of one of his comrades working close by him. Many of the 
miracidia which enter the skin will not succeed in finding their way 
to the liver, but a few do so. These possibilities of infection are 
repeated every time a man urinates into the water. They are 
perhaps repeated every day the season of the Nile flood lasts. There 
is thus not only the possibility, but the extreme probability, that 
several miracidia attain their destination at short intervals. 
The worms they give rise to in the liver are of about the ^me 
age. On this supposition, viz., that several miracidia succee m 
N 
