42 Bepoii of the Billiarzia Mission in Egypt, 1915 



sheep, dogs (possibly rats), geese, ducks, chickens, and crows. 

 Man and cattle were the most obvious sources of contamina- 

 tion of the canal water, and as each was a known host of species of 

 Bilharzia, the probabihties were that cercaria normally developed 

 in them. 



Attempts to infect a calf and a lamb by allowing water heavily 

 charged with the living cercaria to remain in the hollows of the 

 groin for periods of ten to thirty minutes on several days gave 

 entirely negative results at the post-mortems some weeks later. 

 It was noted, however, in the case of the lamb, that the skin, 

 where repeatedly exposed to infection, became markedly red. 



A series of experiments was then made on mice, rats, geese, 

 ducks, chickens, crows, and wagtails. The experiments on the birds 

 proved entirely negative. 



A positive result became apparent by June 13 in a young white 

 rat, which had been infected on May 4. A black mouse which had 

 been infected on May 2 died on June 24 with a number of Bilharzia 

 worms in the liver and mesenteric veins. 



In these early successful infections the mice and rats died from 

 the occlusion of the portal system before the Bilharzia w^orms 

 had reached sexual maturity. A comparative study of mature 

 specimens of Schistosoma hovis and S. hcEinatohium. showed that 

 these two species are so closely allied that, when experimentally 

 reared in an abnormal host, a differential diagnosis could only be 

 made with certainty upon the characters of the fully grown worms, 

 and especially upon those of the egg shell. Further experiments 

 were made. In those animals which survived for seven to eight 

 weeks, female worms were found containing the characteristic 

 eggs (fig. 20). This placed the diagnosis beyond question. 



The animals used were variegated mice and white rats brought 

 from London and fed solely on oats and filtered water. They had 

 been kept in the laboratory under conditions entirely precluding the 

 possibility of unobserved infection. 



Animals found SrscEPTiBLE to Infection. 



In addition to tame white rats and variegated mice, the Egyptian 

 desert rat, obtained from the neighbourhood of the Pyramids, w^as 

 found to be susceptible to experimental infection, while guinea-pigs 

 were pecuharly so. Mangaby monkeys died of acute bilharziosis 

 within two months of infection. Experiments were not made on dogs 

 owing to the quarantine difficulties that would have arisen on our 

 return to England. At the conclusion of its field work the Mission 



