86 
Bilharziasis 
other trematode. Unfortunately, it is quite possible that the sporocysts and 
cercariae found are common in the snails and that the urine added to the 
water did not really infect them.” In 1916, during the months of February 
to June, I collected and examined 500 specimens of this genus of fresh-water 
snail from various parts of Natal. Some of these were infested with cercariae; 
but I found cercariae, typical of Bilharzia infection, possessing a divided tail 
and showing no muscular pharynx, only in specimens from two bathing- 
places which are known to be associated with Bilharziasis amongst swimmers. 
The sporocyst which contained the cercariae which Dr Warren found in 
the specimens of snail he had exposed to Bilharzia infection was an elongated 
body without oral sucker or alimentary canal. Through its transparent walls 
could be seen a large number of cercariae in various stages of development. 
When teased out and stained, the cercariae were seen to consist of a body and 
a tail. The body possessed a terminal oral and a ventral sucker. There were 
no pigment spots and no muscular pharynx. The tail was bifid. There was 
no cuticular keel along either side of the prongs of the tail. 
In a stagnant pool near Durban which is known to give rise to Bilharziasis 
amongst bathers, I have found 15 sporocysts answering to this description 
and containing similar cercariae, in specimens of this same snail. 
The appearance of both sporocyst and cercariae corresponded to those 
described by Leiper and Atkinson 1 as characteristic of Asiatic schistosomiasis. 
RECENT RESEARCHES. 
The Bilharzia Mission to Egypt, according to a full report by Lt-Col. 
Leiper 2 , demonstrated that the parasitic worms which gave rise to Bilharziasis 
in Egypt developed from the cercariae which infested certain species of 
fresh-water snails. The Mission found that infection might take place orally 
or cutaneously. The report is illustrated, and one microgram shows the 
cercariae in the act of passing through the unbroken skin of a newly-born 
mouse. Later, Lt-Col. Leiper 3 reported that those cercariae which infest 
specimens of Bullinus (sic) invariably develop into Schistosomum haematobium ; 
whilst the cercariae which infest the Planorbinae of Egypt always produce 
Schistosomum mansoni. 
DISTRIBUTION. 
Practically all the rivers between Pietermaritzburg and the coast are said 
to be infected with Bilharzia, though it would seem that the disease is not to 
be caught at higher altitudes in Natal. During a somewhat extended tour 
of Natal in the spring of 1916, I visited the following places to ascertain the 
prevalence of susceptible fresh-water snails in infected areas. I found speci¬ 
mens of Physopsis africana difficult to obtain in any places except where the 
water was stagnant or slow-running. 
1 Brit. Med. Journ. Jan. 30, 1915. 
2 Journ. Roy. Army Med. Corps, 1915. 
3 Brit. Med. Journ. March 18, 191G. 
