90 T. R. Lewis — Haematozoa in Stomach q/Culex Mosquito. [M-ViicF, 



specimens obtained on the next occasion were devoid of the enveloping 

 sheath, which appears to characterise the kind found in man out here, and 

 apparently, according to Dr. Manson, in China also. 



Dr. Spencer Cobbold, F. R. S., the well known helminthologist, has 

 drawn prominent attention to Dr. Hanson's observations in a recent num- 

 ber of the ' Lancet' [12th January], and states his conviction that the 

 Culex mosquito is the intermediary host of the Filaria sanguinis-hominis — 

 the name by which the hsematozoon affecting man is known — and that resi- 

 dence in this insect is necessary for the completion of the filaria life-cycle ; 

 hence the association of the mosquito with elephantoid forms of disease. 

 These circumstances made it therefore a matter of some interest to endea- 

 vour to learn whether enquiries of a like kind in India would prove 

 equally conclusive in showing that one of the commonest of tropical and 

 sub-tropical insects acted as a disseminator of blood parasites in man, and 

 steps were taken to ascertain whether it could be shown definitely in this 

 country also that the particular worms in question underwent undoubted 

 developmental changes in the stomach of the mosquito. 



On a future occasion I hope to give a detailed account of these ob- 

 servations ; but, perhaps, it may be deemed sufficient on the present occa- 

 sion to give in a few words the general results of the experiments so far as 

 they have been proceeded with. Notes have not been made of all the 

 insects examined, but out of 140 female mosquitoes [as is well known, it is 

 the female and not male which preys on our capillary circulation] regarding 

 the examination of which record has been kept, 20 were found to contain 

 hsematozoa mixed with the ingesta in the alimentary tube — i. e., equal to 

 about 14 per cent. The method adopted has been to collect groups of 

 insects daily and to set them aside for subsequent observation, a few living 

 specimens of each group being examined at stated intervals. The alimen- 

 tary canal with its contents was removed from the other tissues and the 

 examinations conducted separately so as to avoid, as far as possible, the 

 risk of confounding any developmental changes which might occur in the 

 blood parasites with other parasites which might also be harboured by the 

 insect, for mosquitoes like other insects occasionally harbour different 

 kinds — three or four, what appear to me to be different varieties, have been 

 met with in the course of these examinations. It is of prime importance 

 in enquiries of this kind to be guarded in concluding that because two or 

 more parasites may be associated they are genetically connected ; on the 

 other hand it must not be forgotten that it has often happened that 

 parasites have been classified as distinct which should have been described 

 as different stages in the development of the same animalcule. 



When the insect is caught shortly after feeding and the contents of 

 its stomach examined microscopically, the hsematozoa, if present, will be 



