METAMORPHOSIS OF FILARIA BANCROFTS COBB. 53 



the body-cavity, get into water only on the death of the host, and 

 that they are taken into the human body with the water. This 

 statement still requires demonstration, but even were this proof 

 forthcoming there would yet remain a possibility that the embryos 

 evacuated with the urine (which probably no more represent a 

 useless production than the eggs of intestinal worms which pass 

 out with the faeces) may be transported to certain small hosts, 

 and by these means human beings may perhaps be infected more 

 commonly than in the way pointed out by Manson." 



From these remarks it would appear that Leuckart imagined 

 that it was a normal occurrence for embryo filarise to pass out of 

 the body with the urine ; such is not so, however, and is by no 

 means common in those affected with filariasis ; it occurs in cases 

 only when there is rupture of a lymphatic or blood vessel in the 

 kidney or bladder ; the filarise when mixed with urine are rapidly 

 altered by endosmosis or exosmosis and live but a short time. 

 The same applies to dogs affected by the Filaria immitis in which 

 however it is even of rarer occurrence. 



How did it come about that Manson saw the final stage of the 

 metamorphosis in mosquitoes seven days old ? 



This I believe to be the explanation : — The filariated mosquitoes 

 upon which he made his observations were not bred out and thus 

 in confinement from the moment of their emergence from the pupa 

 state; they were free mosquitoes obtained from a room where 

 filariated persons slept. A few of the mosquitoes that were 

 captured doubtless had imbibed blood weeks before and already 

 contained advanced stages of the metamorphosis. They were 

 imprisoned and never fed, consequently they died about the sixth 

 or seventh day, when they were microscopically examined. 

 Manson evidently believed that their last meal of blood was their 

 first. 



Manson has remarked 1 " that various stages of the metamor- 

 phosis were occasionally to be seen in the same mosquito. 5 ' Such 



1 Op. cib., p. 379. 



