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XIII. The Metamorphosis 0/ Filaria sanguinis hominis in the Mosquito. By Patrick 

 Manson, M.D., Song Kong. Communicated by Dr. Cobbold, F.B.S., F.B.S. 



(Plate XXXIX.) 



Eead March 6th, 1884. 



>IX years ago I described the metamorphosis undergone by the embryo Filaria san- 

 guinis hominis in the body of the mosquito *. I hoped that (considering the practical 

 importance of a correct knowledge of the life-history of this parasite) the statements I 

 :hen made would, long ere this time, have been thoroughly confuted or confirmed. If 

 we judge from the wideness of its distribution and the grave character of the diseases it 

 rives rise to, the Filaria sanguinis hominis is infinitely the most important of the animal 

 parasites attacking man, much more important than Trichina or Echinococcus. Bio- 

 logically the story of its life- history is interesting, and even more wonderful than is that 

 of either of these parasites. Nevertheless, although from both a practical and a scientific 

 point of view it is important to have this assertion of mine about the role of the mosquito 

 cleared up, it still remains but half confirmed, half believed. 



With the exception of Lewis in India f, Myers in Pormosa %, and Sonsino in Egypt §, 

 I do not know that any one has worked seriously at the subject. And although both 

 Lewis and Sonsino have confirmed my statements as to the entrance of the Filaria into 

 the mosquito, and followed up part of the metamorphosis, neither of them has advanced 

 his observations so far as to be able to confirm my statements as to the later stages of 

 this, or positively to prove that the mosquito is, or is not, the intermediary host. 



Some eminent helminthologists in England accept my statements and endorse the 

 inferences I have drawn — Cobbold for example. But in other quarters, so far from 

 securing acceptance of my theory, the work of Lewis, on account of the hesitation and 

 scientific caution with which he expresses himself, has had the effect of inducing a 

 certain amount of scepticism. Leuckart is sceptical; and of course the scepticism of 

 so eminent an authority is of great weight in influencing opinion, especially in Germany. 

 Some of our own zoologists, also, I understand, share the views of Leuckart. 



Recently I received a copy of a lecture by Mr. B. Scheube of Leipzig entitled ' Die 

 Pilaria Ivrankheit.' In this very excellent lecture occurs the following passage : — " Der 

 englische Parasitolog Cobbold hat Manson's Ansicht von der Entwickelung der Filaria 

 sanguinis hominis adoptirtund auf die Analogie mit der Filaria medinensis hingewiesen, 

 welche ihre Metamorphose im Siisswassercyclopen durchmacht. Von Leuckart || 

 dagegen werden gegen die Manson'schen Beobachtungen aus mehreren Griinden starke 



* Proc. Linn. Soc. March 7th, 1S78. China Customs Medical Eeports, Sept. 1877. 

 t 14th Ann. Eep. of the Sanitary Commissioner with the Government in India. 

 + China Customs Medical Reports, March 1881. 21st issue. 

 § Medical Times and Gazette, May 13th, 1SS3, p. 404 ; Sept. 22nd, 1883, p. 340. 

 || ' Die Parasiten des Menschcn,' I. 2. Aufl. p. 85. Leuckart's Jahresbericht fiir 1875-70, p. 163. 

 SECOND SERIES. — ZOOLOGY, VOL. II. 54 



