36 MANSON'S DISCOVERY 



Having thus proved that tlie fihirife were taken 

 up by the mosquito in its meal of blood and that tliey 

 were not killed, he next set to work to find out whether 

 they underwent any changes in the body of the 

 mosquito ; this he succeeded in doing. 



JNlanson observed that when the human blood 

 entered the stomach of the mosquito, it became 

 thickened in consequence of the water wliich it con- 

 tained becoming absorbed. The filaricK which found 

 themselves imprisoned in the stomach of the mosquito 

 became actively motile. After a series of patient 

 dissections Manson was able to trace them through the 

 stomach wall into the abdominal cavity, and then into 

 the thoracic muscles of the mosquito. iMore than that, 

 " I ascertained," adds Manson, " that during the 

 passage the little parasite increased enormously in size. 

 From measuring about yj^ of an inch in length it grew 

 to about -j~r of an inch, and it was now just visible to 

 the naked eye. It developed a mouth, an alimentary 

 canal. Manifestly, it was on the road to a new human 

 host." 



When this state of development was reached in the 

 mosquito, Manson supposed that the latter in all proba- 

 bility died, and that the developed filaria escaped into 

 and infected the drinking water. He supposed that 

 the infected drinking water infected man. Later, 

 however, he succeeded in tracing the filaria a further 

 stage in the mosquito. From the tlioracic muscles 

 he found that the parasite wandered towards the pro- 

 boscis of the insect, and could be found in the sheath 

 of that organ, where it remained to await an opportunity 



