METAMORPHOSIS OF FILIARIA BANCROFTI, COBB. 51 



The young filarial are generally only to be found in the thorax, 

 yet a few occur in some instances in the abdominal cavity. There 

 are usually three or four filarise present, sometimes as many as 

 twenty-five. In twenty filariated mosquitoes that were killed and 

 examined between sixteen and sixty days, every one of them con- 

 tained actively moving filarise. 



Mosquitoes bearing filarise do not appear to be injured seriously; 

 one that was killed fifty days after its meal of blood contained 

 eleven filarise in the thorax and two in the abdominal cavity. 



In mosquitoes fed on non-filariated blood no filarise could be 

 detected. 



When the mosquito's thorax is torn across several times with 

 dissecting needles in a watch-glass containing water on the stage 

 of a dissecting microscope, the filarise are liberated and sink to the 

 bottom ; they can be seen fairly easily with the naked eye and by 

 aid of a needle picked out ; they cannot swim nor move away 

 from the spot where they happen to sink, yet they twist and 

 wriggle about in a violent manner ; by means of what appear to 

 loe caudal suckers some of them stick to the glass, also to the 

 dissecting needle when touched by the same. 



Water is injurious to them for after three or four hours therein 

 they die. Water therefore cannot be the medium, as was gener- 

 ally supposed, by which they ultimately reach the human subject. 



Directly after having seen the first " actively moving filarise " 

 wriggling about in water for a couple of hours, I concluded that 

 water was the medium, and wrote a letter to the Editor of the 

 Australasian Medical Gazette 1 to that effect, being anxious to 

 correct a former statement 2 of mine to the effect that the young 

 filarise died in water ; [as subsequent observation has shewn that 

 statement did not require correction]. Shortly after having 

 written the letter I found the young filarise were dead but con- 

 cluded that they must have been injured by the cyanide of 

 potassium by which the mosquito was killed. Many experiments 



1 Australasian Medical Gazette, March 20, 1899. 2 Ibid., June 20, 1898. 



