FILARIA SANGUINIS HOMINIS IN THE MOSQUITO. 381 



Frequently during my study of the metamorphosis in the mosquito, it has occurred to 

 me that the later stages of what I describe as the Mlaria of man in the mosquito, may 

 really be stages in the development of a purely insect parasite like Gorditis or Mermis, 

 ',and not the Mlaria sanguinis hominis at all. Perhaps, I conjectured, this animal may 

 escape from the body of the mosquito into water, where it may acquire organs of genera- 

 tion and breed, and its young may afterwards enter the body of the mosquito larvae, and 

 so complete the cycle. But if this is the case, there must be a time in the histories of the 

 human Mlaria and this hypothetical animal when it is impossible to discriminate between 

 them. I have never been able to find a break in the chain of development. 



Moreover, if the mosquito is liable to be infested by a nematode parasite peculiarly its 

 own, and if the developmental forms I have been describing belong to such a parasite, 

 then we ought to find them in mosquitoes that had fed on non-filariated, as frequently 

 as we find them in mosquitoes fed on filariated blood. If one filarial form could be 

 tbund in a mosquito fed only on non-filariated blood then my theory about the role of 

 this insect is in danger of falling to the ground. 



This is a point I gave some attention to. Simultaneously with observations on 

 mosquitoes fed on the blood of my filarious subject, I carried on others on mosquitoes 

 saught in the mosquito-nets of coolies and servants living in my house. The result was 

 pery striking. I carelessly assumed that my servants were free from Mlaria, and did not 

 3xamine their blood, but trusted to the mosquito to pick out for me those who might be 

 Eilarious. 



Two mosquitoes were brought to me by coolie No. 1. One of these I examined at 

 Dnce — no Mlaria ; the second I kept till the fourth day before examining it — no Mlaria. 



Coolie No. 2 brought two mosquitoes. I examined one on the first day but found no 

 Filaria in the blood in the abdomen. The second I kept till the third day. I examined 

 ts thorax very carefully, and then had the mortification of finding a sausage-shaped body 

 exactly like that represented at fig. 12. There could be no doubt about its nature. I 

 ;hought my theory was upset, and all my work useless. At 9 p.m., however, I examined 

 olood drawn from this man's finger, and had the satisfaction of finding in it plenty of 

 Filarim ; subsequently he contributed Mlaria-chavgeA mosquitoes for my investigation 

 »f the metamorphosis. The mosquitoes he brought me were often devoid of Filarice ; he 

 jvas a lazy man, slept much during the day, and in a very dark room such as mosquitoes 

 iffect even during the day, hence many of the insects he found in his net were charged 

 vith blood drawn at a time when the Filaria is not in the general circulation. 



Coolie No. 3 brought on one occasion two, and on another occasion five mosquitoes. 

 Their examination gave this result : — 



Mosquito examined on 2nd day No Filaria. 



„ „ on 3rd day „ 



„ „ at 74 hours ,, 



,, at UG hours One sausage-shaped Mlaria. 



n „ Two Filarice. 



„ „ Many Filarice. 



„ Several Filaria. 



Again my theory seemed doomed to collapse. But I examined the man's finger- 



