236 OUR HOUSEHOLD INSECTS 



body of one host, and their later life in that of another. 

 Numerous experiments and investigations, by Dr. Manson 

 and others, seem to have proved that such a connec- 

 tion exists between man and a particular kind, or some 

 few kinds, of mosquito. The parasite is called Filaria 

 sanguinis hominis (the thread-worm of the blood of man). 

 The adult female of this creature inhabits the lymphatic 

 glands of man, and is the cause of the curious and re- 

 pulsive disease called elephantiasis, and of kindred 

 maladies. Embryos produced from these sexually 

 mature forims, pass from the lymphatic system into the 

 blood of man, and circulate with it, causing in this stage 

 certain kidney diseases. No forms intermediate between 

 these two have been found in man, and it is therefore 

 evident that the intervening stages of the life of the 

 parasite, whatever they may be, are spent elsewhere. 

 From the blood of man, the embryos pass into the 

 body of the mosquito as it sucks its victim. Only a few 

 of these seem to be digested with the blood; the rest 

 escape from the mosquito's digestive tube, and establish 

 themselves in its thorax, at the same time undergoing 

 a change of form indicative of an advance in develop- 

 ment. Thus far the history of the parasite has been 

 traced, but exactly what happens afterwards is still to 

 some extent a mystery. The mosquito infested with 

 Filarice appears soon to die, the parasite apparently sub- 

 sisting on the contents of its thorax. It has been 

 thought that the mosquito's body falling into the water 

 on its death, the parasites escape and pass a free exist- 

 ence for a time, being after a while re-introduced into a 

 human host by the drinking of the water that contains 

 them. In investigating these facts, Dr. Manson got a 

 Chinaman whose blood was known to contain Filarice, 

 to sleep in a small curtained chamber, placed in a larger 



