248 p. MANSON ON FILARIAL MIGRATIONS. 



Foreigners are not so partial to water drinking as are the natives ; 

 at least when water is drunk it is usually qualified with wine or 

 spirits, and serated waters of different kinds are in general use. The 

 most careless foreigner and the total abstainers seldom drink un- 

 filtered water ; and if filtration cannot exclude an animal at least 

 the thirtieth of an inch in length, the passing of water through a 

 filtering apparatus must be regarded as a meaningless ceremony. 



It is to be regretted that Dr. Somerville has not been more ex- 

 plicit as to the number of natives whose blood he has examined for 

 filaria. Dr. Eennie, of Foochow, writes me he frequently sees the 

 parasite in his hospital cases. Readers of Lewis' earlier papers will 

 remember the warning he gave, foreseeing such criticisms as Dr. 

 Somerville's. He says, referring to accounts of chyluria cases, such 

 remarks as this will be frequently recorded, ** Filaria searched for 

 but not found " — or words to that effect. 



If the examination of filarious blood is made during the night it 

 is almost as easy to find the parasite as it is to find a white blood 

 corpuscle. Seeing this, and the frequency with which the presence of 

 the parasite is associated with lymphatic fever, elephantoid and other 

 disabling affections, I have sometimes thought it would be worth 

 the trouble for the Government in India to institute the systematic 

 examination of the blood of native recruits by their medical officers. 

 I am satisfied that by the rejection of filarious subjects much in- 

 validing and expense might be avoided, and that, too, at very little 

 trouble. At any rate much useful information might be got 

 together, and such an idea might be profitably ventilated by Sir 

 Joseph Fayrer, or some other Indian authority. 



You may use this letter as you think best. 



Yours faithfully, 



Patrick Manson. 



