XII] DESCRIPTION 2O5 



absent. The anterior end is rounded and not marked off from 

 the rest of the body by a distinct neck as in the case of the 

 female. 



The embryos, or microfilariae as they are frequently termed, 

 occur in the peripheral blood. Manson describes the move- 

 ments of the living parasite in the following words : "In fresh 

 blood, F. nocturna (= bancrofti) is seen to be a minute, trans- 

 parent, colourless, snake-like organism which, without materi- 

 ally changing its position on the slide, wriggles about in a state 

 of great activity, constantly agitating and displacing the cor- 

 puscles in its neighbourhood. At first the movements are so 

 active that the anatomical features of the filaria cannot be 

 made out. In the course of a few hours the movements slow 

 down, and then one can see that the little worm is shaped 

 like a snake or an eel that is to say, it is a long, slender, 

 cylindrical organism, having one extremity abruptly rounded 

 off, the other for about one-fifth of its entire length gradually 

 tapering to a fine point. When examined with a low power, it 

 appears to be structureless ; with a high power, a certain 

 amount of structure can, on close scrutiny, be made out. 

 In the first place, it can be seen that the entire animal is en- 

 closed in an exceedingly delicate, limp, structureless sack, in 

 which it moves backwards and forwards. This sack or 

 " sheath " as it is generally called, although closely applied 

 to the body, is considerably longer than the worm it encloses, 

 so that that part of the sack which for the time being is not 

 occupied is collapsed, and trails after the head or tail or both, 

 as the case may be. It can be seen also that about the posterior 

 part of the middle third of the parasite there is what appears 

 to be an irregular aggregation of granular matter which, by 

 suitable staining, can be shown to be viscous of some sort. 

 This organ runs for some distance along the axis of the worm. 

 Further, if high power be used, a closely set, very delicate 

 transverse striation can be detected in the musculo-cutaneous 

 layer throughout the entire length of the animal. Besides 

 this if carefully looked for at a point about one-fifth of the 

 entire length of the organism backwards from the head end, 

 a shining triangular V-shaped patch is always visible. This 



