OBSERVATIONS ON FILARIA. 67 



malarial fevers. It is marvellous how Xatm'e has adapted the 

 habits of the Filaria to tliose of the mosquito — the embryos are in 

 the blood just at the time the mosquito selects for feeding. 



" Another fact in adajotation you might like to know. The long 

 lash on the tail of the embryo has a meaning in relation to its 

 future life. I think so from the following experiment. Drop a few 

 fibres of cotton into the fluid of a milk (filarious) hydrocle. 

 They will subside to the bottom of the vessel very gradually. 

 Leave them there for a few minutes, and then place them 

 under the microscope. You will find them beset by thousands 

 of embryos in rows and clusters, each embryo attached by its tail 

 lash as one can attach a whip to a rope by striking it sharply with 

 the lash. When the mosquito penetrates a blood vessel, the passing 

 embryos lashing about, as is their habit, entangle themselves thus 

 on the proboscis, and get sucked up. Hence the enormous numbers 

 of embryos in the mosquito's stomach and the secreting faculty of 

 that insect. 



" It would be well to warn observers against concluding that a 

 case is non-filarious from observations made during the afternoon, 

 and that the most reliable time to make them is at night, and, if 

 possible, they should employ a mosquito to make it for them. In 

 consequence of my ignorance of this particular point in the history 

 of the parasite, my statistics as to its prevalence in Amoy and neigh- 

 bourhood lose much of any value they may have been supposed to 

 possess. If I can find the time I may go over the ground again, 

 making examinations after sunset instead of, as formerly, between 

 5 a.m. and 6 p.m. 



" The following are the particulars of the case belonging to tlie 

 mosquitos and Lymph scrotum I send you ; I copy them verbatim 

 from my note book : — 



' F. S. H. — Lymph scrotum and Eleph. scrot. insipient. Oah. 

 M. ; a^t. 19 ; Khoan Kaw, Eong ; a rice miller. Parents dead; 

 no relatives with elephantoid disease as far as he knows. Eong is 

 a small hamlet of about a hundred inhabitants in the suburbs of 

 Khoan Kaw, Elephantiasis he has often seen in Khoan Kaw. 

 Drinks well water stored sometimes for several days in a large 

 jar. When 16 or 17, sometimes sick with an evanescent fever and 

 relapsing inflammation (it may be of the testicle) of the right side 

 of the scrotum, accompanied by enlargement of right and left groin 

 glands, especially of right. When 15, had an abscess in left groin 



