F. Gr. Cawston 
85 
In the Tropical Diseases Bulletin , March 30, 1914, Fleet Surgeon Kumagawa 
comments on the publication of K. Mirairi and M. Tuzuki 1 . “The authors 
noticed that, when ox faeces which contain the eggs of Schistosomumjaponicum 
are kept for one or two hours in a suitable temperature, mixed with water, the 
majority of the miracidia come out, breaking the shell and swimming about 
very vivaciously. They noticed also that, in the infected locality, there are 
many snails in the waterways and ditches.” The authors carefully picked up 
a number of young non-infected snails and tried whether the miracidia entered 
their bodies or not. They found that the miracidia entered the body of the 
snail. After twelve days the first rediae appeared and gradually concentrated 
to the hepatic ducts. The authors put mice into the vessels in which the full- 
grown snails were fed for three hours every day, and repeated this experiment 
for four days. After three weeks they found a great many Schistosomum 
japonicum in the livers of the mice. The authors concluded that this kind of 
snail was an intermediary host of Schistosomum japonicum. These observations 
were confirmed by the Wandsworth Expedition of the London School of 
Tropical Medicine, in the spring of 1914. 
EXPERIMENTS IN NATAL. 
In May 1915 I made repeated attempts to infect specimens of Limnaea 
natalensis with miracidia obtained from recently passed urine. There was 
practically no possibility of these fresh-water organisms being infected with 
Bilharzia when the experiments were commenced, nor could any evidence of 
infection be detected at the end of several weeks. These experiments were 
repeated in September, but again with negative results. From further study 
I am of opinion that Limnaea natalensis is not susceptible to infection with the 
miracidia. 
Judging from the reproduction of digenetic trematodes, Dr E. Warren, 
the Director of the Natal Government Museum, was of opinion that the 
miracidia had the asexual phase of its development in the mollusca; that it 
would die if unab ] e to harbour in a suitable mollusc in 24 to 48 hours and 
that, if it was able to migrate to the liver of a mollusc, the sporocyst—a 
smooth-walled elongated sac—would develop in the course of a week or two. 
He expected to find the sporocyst giving rise by budding of its wall to 
daughter-sporocysts and to contain a large number of cercariae with bifid 
tails. 
At the end of May 1915, I supplied him with urine obtained from a patient 
suffering from Bilharziasis. He diluted this urine, which swarmed with ova, 
and added it to a vessel of water containing snails, Physopsis africana. The 
bathing season had not commenced and the snails were probably free from 
infection when the experiments began. Four weeks later, he wrote me a 
letter in which he said: “I have found some undoubted cercariae in infected 
snails, and the question now is whether they belong to Bilharzia or to some 
1 Tokio Mtd. Journ. Sept. 1913. 
