Traii.si)iis,sl(tii 7 



Cobbold. His experiments, begun in 1870, were made in England 

 with eggs obtained from persons who had returned from South 

 Africa with hoematuria. These experiments, which proved negative, 

 are recorded in an article [101] " On the Development of Bilharzia 

 hcematohia," in 1872, in the following words : — 



" I naturally sought for the possible intermediary bearers of 

 Bilharzia among fresh-water molluscs and small Crustacea. . . . 

 I tried to induce the ciliated embryos to enter into the bodies of a 

 great variety of animals such as gammari, dipterous larvae, entomos- 

 traca, limnaei, paludina3, different species of planorbis, and other 

 fresh-water molluscs, but neither in them nor in sticklebacks, roach, 

 gudgeon, or carp, did they seem inclined to take up their residence. 

 These experiments, however, are by no means conclusive, since the 

 conditions under which the experiments were made departed in 

 several respects from those that are presumably essential to success 

 in the ordinary course o£ Nature." 



The first, and in many respects the most sustained effort to 

 elucidate the problem in an endemic area was made by the Italian 

 helminthologist Sonsino, principally during the last two years of 

 bis stay in Egypt from 1874 to 1885. 



The report of his " Eicerche sullo sviluppo della Bilharzia 

 Hoematobia," issued in 1884 [462], shows that Sonsino's investi- 

 gation followed upon rightly conceived lines. Having accepted 

 Chatin's view that the presence of germinal cells in the ciliated 

 embryo indicated preparations for a metamorphosis as in other 

 trematodes, he attempted, in the endemic area : — 



{a) To infect, experimentally, mollusca kept in an aquarium. 



(6) To find larval Bilharzia naturally infecting some species 

 of mollusc or insect. 



The following species are definitely listed as giving negative 

 results— (a) to experimental infection: Vivipara unicolor, Cleopatra 

 cyclostomoides, Cleopatra bulimoides, Physa Alexandrina, and 

 Melania tuberculata, and (h) to dissection: Vivipara unicolor, 

 Cleopatra cyclostomoides, Cleopatra bulimoides, Physa Alexan- 

 drina, Melania tuberculata, Physa micropleura, Physa Innesi, 

 Limnaea natalensis, Planorbis schweinfurthi, Unio campanii, 

 Unio Jickeli, Corbicula spp., and Spatha caillaudi. 



The dissections revealed, however, a large number of trematode 

 larvae in the molluscs of Egypt. These developmental forms were 

 described in a notable comnmnication in 1892 [472]. 



From these investigations Sonsino concluded that " non e ^- 

 improbabile che la bilhari/ii che per tante particolarita s'allontana 



