239 



On the Periodicity of Filarial Migrations to and from 

 THE Circulation. 



Bj Patrick Manson, M.D., Anioy. [Commiiaicated by Dr. 



COBBOLD.] 

 {Read January 28th, 1881.) 



PLATE XIX. 



Amoj, 25tli August, 1880. 

 T. Spencer Cobbold, Esq., F.R.S. 



Dear Sir, — I read with mucli pleasure the notice in the 

 " Lancet," 3rd July, of your communication to the Quekett Club 

 respecting the specimens I sent you. 1 note that the bird parasites 

 are new species, and I am much gratified to learn that the Distoma 

 of Dr. Ringer is new also, and is to bear that gentleman's name. As 

 I did not make any examination of the Distoma Ringeri, fearing to 

 mutilate too much the solitary specimen, I would like to see any de- 

 scription of it you may publish. 



The reprint from Vol. VI. of the " Quekett Club Journal " I 

 duly received, and I thank you for the trouble you have taken in 

 thus bringing forward my work. In reading it I was especially in- 

 terested in the short note by Dr. Mortimer Granville. Though his 

 speculations are founded on an error, yet I like the scientific style in 

 which he treats the subject. Perhaps you will show him the chart 

 I send you herewith. He would see from it — 1st. That the 

 periodicity observed by the filaria embryos is by no means an ex- 

 ceptional or capricious phenomenon ; and, 2nd, that it is associated 

 with the advent of night, and not depending in any way on the 

 sleeping state. 



Although in the paper I sent you some time ago I refrained from 

 speculating on the cause of filarial periodicity (because I had nothing 

 but guesses to offer), yet I have thought a good deal about what 

 might be the reason of this most remarkable phenomenon, which, as 

 you say, " savours of the marvellous." As Dr. Mortimer Granville 

 remarks, it is well deserving the attention of physiologists, for could 



