62 OBSERVATIONS ON FILARI.E. 



these facts in relation to the etiology of malarial fevers, and he 

 concludes his letter — for such it only pretends to be — by 

 stating his determination to carry on the investigation until the 

 whole body of available facts is explored and the results, in all their 

 professional bearings, are elucidated. 



It remains for me to observe that this novelty in helminthology 

 savours somewhat of the marvellous. When the facts come to be 

 fully understood, I think it will appear that neither the parasitism 

 of Trichinaf nor that of Echinococcns approaches in interest that 

 of the human Filarice. Probably millions of victims exist in 

 tropical countries ; many of them suffering from grave dis- 

 orders consequent upon this invasion of their tissues. That in the 

 face of such astounding facts as have of late years come to light 

 there should be found professional men of standing averse to 

 encouraging researches of this kind is one of those retrograde social 

 phenomena which I greatly dc^plore ; but where the interests of 

 humanity are so much concerned such disparagement ought not to 

 be allowed to check our efforts. 



It must be obvious to every one that naturalists, physiologists, 

 and medical men will separately view these discoveries from very 

 different standpoints ; and it will need some master mind to collate 

 all the phenomena in relation to cause and effect. At present 

 I have only had opportunity to converse at any length with one 

 physician on the subject. In the opinion of Dr. J. Mortimer- 

 Granville we must not look for a solution of the phenomenon of 

 periodical local migration as arising from any special want on the 

 part of the entozoon, but rather as arising from varying physiolo- 

 gical conditions affecting the host. Whether this view be correct 

 or otherwise, I think Dr. Granville's suggestions highly important ; 

 and as he has been good enough to communicate an abstract of 

 them in writing, I append them to this introduction in the form of a 

 separate commentary. 



The communication of Dr. Somorville has more especial reference 

 to the closely allied microscopic Filarice infesting the dog. The 

 adult Filaria imniitis engaged my attention at Edinburgh some 

 thirty years ago ; but, in recent times, Dr. Somerville was, I 

 believe, the earliest to report on this subject in the Customs 

 Gazette. He believes that the occurrence of Filaria sanguinis 

 honiinis at Fuchow to be comparatively rare ; but, in this case, 

 as probably obtains in many others, the negative indications may 



