178 
thus forced to the conviction that Man himself aciiij 
intermediary host. 
If this conclusion is correct it leads to the important consequrncr 
that the spread of the Sc A. hamatobium is not 
limited by the natural geographical distn 
bution of a special intermediary host, heu 
spread wherever man carries it, so long as, and in so far as. the 
climatic and hydrographic conditions are favourable for its develop 
ment. With regard to this point, I entirely disagree with Sr 
Patrick Manson who says (1907, p. 653) that the peculiar geogn 
phical limitations of Sch. hesmatobium are difficult to explain if i 
does not require the services of an intermediary host. However, I 
also hold that Sch. hcentatobimn is by no means geographically >■ 
limited as it appears to be to the defenders of the existence of 
mansonj. 
No investigator has hitherto succeeded in keeping the rairacida 
alive for more than 30-40 hours; in my personal experiments, tlx 
upper limit found was 28 hours. They must find some new shellrr 
within this time. If they are destined to return into man directiv, tw 
possibilities are, a priori, imaginable, viz., tliat they enter by ihf 
out , or that they enter by the skin. I have found by experimen’. 
hat hydrochloric acid diluted with water to the extent of 
I . 20c^ kills them within 2-3 minutes, a solution of 1 : 1000 almov 
enter” I am thus led to the view that tho 
interoreterf ^ ^^^re are some other facts which may b( 
In Man th ^ ''''•I not mention them here 
dLcUv or ‘--cdium must develop into a sporocyst which, either 
We havr!',"'?’ --- 
far knowT^to 
young, worms is the liver ““otiraes ve^ 
habitat of tlie ^h^r^from conclude that the liver is tbe 
port^v^L later escape .nto* 
can escape also mto°the°heDTtfr''' 
have been founH rrv P^tic veins. As a matter of fact tbe? 
the lung (Symmers)”£™‘'i?[. ''"a “va (KaRICUS'- 
'■ver Which rhr-eXs.r*’” 
