122 Report of the Bilhar,^ia M/.ss/o?? in Egypt, 1915 



cattle. Female worms found post mortem contained the eggs iu numbers. 

 This result confirmed the earlier find in mice which had been infected by 

 immersion. Other animals gave confirmatory evidence. We had now 

 established experimentally that the cercaria derived from P. hoissiji gave 

 rise to lateral-spined eggs, whilst those derived from Bidlinus gave rise 

 solely to terminal-spined eggs. In both cases infection was restricted to 

 the intestine, but this was probably due to differences in the venous con- 

 nexions of the bladder. Undoubtedly the gut wall was the primitive 

 habitat of all the bilharzia worms. 



The young but sexually mature B. h(Bmatohia, derived from BuUimis 

 infection, were well able to lay terminal-spined eggs. Although the very 

 earliest efforts did not conform completely in full size and shape to the 

 standard egg, no evidence of a tendency to the formation of eggs with 

 laterall3'-distorted spine was forthcoming. 



To completely clinch the matter, a final experiment seemed desirable. 

 Animals — monkeys and rats — were infected very lightly with P. hoissiji 

 cercaricB and kept alive for nine months. The living female worms, found 

 post mortem at the end of that period were still producing lateral-spined 

 eggs ; one or two only at a time. For these coupled worms, the 

 " transition period " must surely have long since passed. 



The terminal-spined and lateral-spined eggs found in bilharzial infec- 

 tions are, therefore, the normal and characteristic products of two distinct 

 species, B. hcBmatohia and B. mansoni, and are spread by different inter- 

 mediary hosts. The young females in each species produce slightly atypical 

 eggs, but these slight variations do not "form a continuous series of inter- 

 mediary stages between the two types." 



As transmitter of the parasite of urinary bilharziosis in Egypt, Bidlinus 

 fulfils all requirements as far as distribution is concerned. It is found in 

 the larger canals, in the smaller irrigation channels and finally, in the 

 village ponds or " birkets." B. hcBmatobia cercaricB have been found in the 

 species B. contortus, B. dijhoiosTii, and once in a specimen which was 

 recognized as B. innesi. These species would appear to correspond to the 

 forms named Physa alexandrina by earlier workers. 



The more restricted distribution of Planorbis hoissyi would appear to 

 correspond equally satisfactorily with the less universal occurrence of 

 intestinal bilharziosis due to B. mansoni in Egypt. In the course of this 

 inquiry, it was not found in the large canals or in the village "birkets." 

 It appeared to frequent the smaller irrigation channels and drains where 

 these were permanent. It was found also in marshes. Both carriers were 

 found susceptible to drying, Bidlinus extremely so. 



The intermediate host of B. hovis remains to be discovered. This para- 

 site was first found by Sonsino at Zagazig, some miles north of El Marg. 

 Several animals were seen infected at the Cairo abattoir, but the majority 

 of these came from the south. The veterinary inspector in charge informed 

 us that B. hovis was much more common in Sudanese than in Egyptian 

 cattle. 



