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larvae than with those of the other two species. It has been 

 shown experimentally that larvae of //. microstoma, although 

 being able to set up a typical reaction with necrosis, quickly 

 disappear in the tissues. If "swamp cancer" be due to the 

 larval form of H . microstoma, it seems possible that this is one 

 of the reasons for the failure so far to demonstrate the pres- 

 ence of any larvae in the tissues. Also, as the presence in the 

 skin of larvae of H . microstoma would apparently depend upon 

 their inoculation by Stomoxys calcitrans, a super-infection 

 would at least be uncommon ; therefore, one would not expect 

 to find larvae only a few days old in an ulcerated lesion, as 

 is possible in those due to the larvae of other species of 

 Habronema. If "swamp cancer" is due to the final larval 

 stage of H. microstoma as seen in Stomoxys calcitrans, then 

 the probability of its demonstration in the lesions would 

 appear to be somewhat remote. 



It seems possible also that "6wamp cancer" may be due to 

 other species of Habronema carried by some other form of 

 muscid such as Musca vetustissima, which may be found 

 further afield than Musca domestica. If M. vetustissima were 

 responsible one would expect to find lesions in the conjunctiva. 

 As far as one is aware these have not been observed, nor have 

 the lesions been observed on other external mucous membranes. 

 Lesions have, however, been observed on the sheath and limbs, 

 sites commonly attacked by Stomoxys calcitrans , so that the 

 suggestion that this fly may be responsible seems more likely to 

 be true than the latter suggestion. 



The observations and experiments made by Lewis are of 

 importance. He has shown that "swamp cancer" occurs on 

 those parts of the body commonly attacked by Stomoxys 

 calcitrans. He has discussed the possibility of "swamp cancer" 

 being due to a verminous infection, but has come to the 

 conclusion that it is improbable. He believes that the 

 eosinophilia observed in the lesions is due to the reaction of 

 the breaking-down epithelium, and calls the reaction a local 

 eosinophilia. 



General eosinophilia may or may not be demonstrable, but 

 in any case the eosinophile leucocytes found in the lesion have 

 to be brought there by the circulating blood. Lewis is not 

 very clear on the distinction he wishes to draw between a 

 general and a local eosinophilia. Apparently he claims never 

 to have found eosinophile leucocytes in the vicinity of 

 verminous parasites. This is contrary to the experience of the 

 present writer. It may be granted, however, that the presence 

 of eosinophile leucocytes in a tissue is not always indicative of 

 the presence of a verminous parasite. 



