196 PAEASITES OF MAN 



open, and funnel-shaped, and from it a delicate line can be 

 distinctly traced passing to an opening near the caudal extre- 

 mity, the tail itself gradually disappearing (s, t). Speaking of 

 the most advanced stage Manson says : ' ' A vessel of some 

 sort is seen in the centre running nearly the whole length of 

 the body and opening close to one extremity. This end is 

 slightly tapered down and is crowned with three or perhaps 

 four papillae, but whether this is the head or tail, and whether 

 the vessel opening near it is the alimentary canal or the vagina, 

 I cannot say/' Now it is quite evident, I think, from Hanson's 

 figures that he has here faithfully represented the head and 

 tail, the former (u) to the left, the latter (v) to the right. In 

 his manuscript (from which I am now quoting) there is no 

 special reference to these two figures ; but it is easy to see that 

 these terminal sections of the body of the advanced embryo 

 closely correspond with the head and tail of the adult worm 

 (Filaria Bancrofti). The curved line passing to the left (u) 

 evidently indicates the commencement of the partially-formed 

 vagina. 



How completely Manson took the initiative in this part of the 

 work is evident even from Lewis's own later observations. In 

 a paper published in March, 1878, Dr Lewis, writing from 

 Calcutta and speaking of the role of the mosquitoes, says : " I 

 had repeatedly examined, in a cursory fashion, these and other 

 suctorial insects, but had not observed any parasites suggestive 

 of these einbryo-haematozoa, hence, when, on receipt of a com- 

 munication from Dr Manson a couple of months ago, a renewed 

 search was made, I was surprised to find that four out of eight 

 mosquitoes, captured at random in one of the servants' houses, 

 harboured specimens of haematozoa to all appearances identical 

 with those found in man in this country. After this, however, 

 several days elapsed before any mosquitoes could be obtained 

 which contained these embryo-nematoids, and the specimens 

 obtained on the next occasion were devoid of the enveloping 

 sheath, which appears to characterise the kind found in man 

 out here, and apparently, according to Dr Manson, in China 

 also." Further on Lewis also remarks, " When the insect is 

 caught shortly after feeding and the contents of its stomach 

 examined microscopically, the haematozoa, if present, will be 

 observed to manifest very active movements, which may pos-' 

 sibly continue for several hours on the slide. If the insect be 

 kept for twenty-four hours before examination it is probable 



