THE FILIARIASES 



275 



The number of adulls necessary to produce ihem is not known. 



One Filaria can live for several years in the human body, and a 

 Microfilaria can live in the blood-stream for several months (Bancroft). 



Its Habits in the Mosquito. — The UKxsquito sucks infected blood; 

 the Microfilaria passes to the stomach, where the sheath is fixed by 

 the surrounding haemoglobin and also altered by the gastric juice. 



Mf. loa: in thick film, dried and 

 stained with hseniatxylin. x 1,000. (After 

 Fiilleborn.) 



Mf. Persians in thicl< film, dried and stained with 

 haematoxylin ; 4, unshrunken ; 5, shrunken, x 1,000. 

 (After Fiilleborn.) 



As a result of these changes the embryo is able to rupture the 

 sheath with its spine and to escape. The stomach wall is then pierced 

 and the embryo passes to the thoracic muscles, where it grows con- 

 siderably during sixteen to twenty days. In this position they develop 

 four lips, an alimentary canal and a three-lobed tail. The position is 

 now changed, and the embryo finds its way to the prothorax, head and 



