118 Beporf of tlie Bilharzia Mission in Egypt, 1915 



caused local irritation due to penetration of the skin in animals exposed to 

 infection by immersion. Thus the earlier parts of this report were written 

 with reference to '' bilharzia," without touching (save inadvertently by the 

 use of '' B. hceniatobia" in the old inclusive sense) on the problem of the 

 unity or duality of the parasite concerned in the causation of bilharziosis. 

 Indeed, the success of these experiments led to a further delay. The lethal 

 effect of very dilute solutions of coal tar derivatives on the cercariae raised 

 the hope that if minute quantities of these substances could be got into 

 the portal system unchanged, they might be found to destroy the bilharzia 

 worms there. Thus, by cutting short the egg-laying period, the subsequent 

 severity and duration of an infection might be considerably diminished. 



Surgeon-General Ford was of opinion that a satisfactory method of 

 treatment might prove of considerable service. Expert co-operation in 

 the pharmacological aspects of the problem was obviously desirable. 

 As soon, therefore, as it was evident that animals were being infected 

 successfully, I decided to infect as many animals as were then available 

 and to return to England to carry on further work on these lines. Infec- 

 tions were accordingly made from P. hoissijl and from Bullinus. It was 

 hoped that these would provide material still needed for the zoological 

 inquiries not yet completed. A return in the autumn was foreshadowed, 

 if facilities were obtainable, in the event of the need arising for further 

 investigations through failure of the material or the upcrop of new 

 problems. 



^ Most of the infected animals survived the homeward 



Experimental . ^ ^_ ^^ ^ , ^ ^ ^, . . ,, • -, ^ 



Treatment journey. Dr. H. H. Dale, F.K.fe., kindly carried out a series 



Negative of tests and the animals were afterwards dissected. It was 



agreed that none of the substances of known anthelmintic 



or cercariacidal value could be introduced into the portal system in doses 



lethal to adult parasites. This cleared the ground for a continuation of 



study of the specific nature of the cercariae found respectively in BuUinm^ 



and Planorhis. 



r^ In addition to the cercaria provisionally identified as 



p. ,. that 01 an avian bilharzia worm, three bilharzia cer- 



', D 77- cariae were provisionally differentiated from material col- 



AND nuLiinus. ^ 



lected at El Marg (figs. 4.5, 46, 47, Part III). Of these, 



one (fig. 4.5) infested P. boissjji; with it, later, but seen much less 

 frequently, was a large form (fig. 4(j). This mollusc was not found in 

 some other villages where bilharziosis was also prevalent. It was, there- 

 fore, apparent that even if eventually it was proved to be a carrier of 

 infection to man, other species of mollusca must also be concerned. The 

 search was therefore continued, and several weeks later, at the commence- 

 ment of June, examples of the genus BuUinus were found to be likewise 

 infested with Bilharzia cercarice of slightly different appearance (fig. 47). 

 As cercariaj, naturally discharged, became available from each som'ce, 

 animals were submitted to infection by immersion, and later by the mouth, 



