272 PROCEEDINGS OF THE ACADEMY OF [1896. 



the West Coast of Africa. Without entering into the details of this 

 most interesting case I will merely state that in two successive 

 operations Dr. Robertson extracted two Filarise (species loa) from 

 the ocular tissues, the first a male the second a female. Both of 

 these adult parasites are described by Manson in the course of 

 Robertson's paper. The female was stuffed with embryos but 

 repeated examinations of the blood failed to detect any embryonic 

 Filarioe in that fluid. This fact seems to refute Dr. Hanson's hypoth- 

 esis that Flaria loa is the adult form of Filaria diurna. 



The fact that the case on which my remarks are based is the first 

 of the kind observed in Philadelphia justifies the publication of a 

 life-history of the parasite, Filaria nodurna, which I found in the 

 blood of my patient and of which living specimens are placed under 

 the microscope. I wish, therefore, to emphasize the fact that Filarise 

 in the blood vessels are undeveloped, embryonic, and that they are 

 the progeny of an adult, two or three inches long, which has its 

 permanent abode in one of the lymphatic channels, probably the 

 thoracic duct. Manson, observing the embryonic characters of the 

 circulating Filarise, came to the inevitable conclusion that they must 

 reach a further stage of development outside of the body and, in all 

 probability, in the interior of some blood-sucking animal. He 

 naturally thought of the mosquito, an insect whose nocturnal blood- 

 sucking habits seemed to render peculiarly fit to act the part of 

 intermediary host. Without entering into details I will merely say 

 that Hanson's hypothesis was fully verified by experiment. 



In the case of Filaria diurna it is conjectured that certain blood- 

 sucking flies of Old Calabar known as Mangrove flies play the role 

 of intermediary host. 



The mode in which the embryos of Filaria perstans are supposed 

 to escape from the human body is equally interesting, although it does 

 not involve the agency of any blood-sucking insect. In the region 

 in which Filaria perdans is endemic there prevails a skin disease 

 called " craw-craw " attended with pustules, in the contents of which 

 Filarise have been found. It is supposed, with great probability, 

 that the embryos escape with the rupture of the pustules and, in 

 some as yet unexplained manner, although probably through the 

 medium of drinking water, gain access to the human system in 

 which one, or more, attain maturity. It must be confessed, how- 

 ever, that our knowledge of the life history of Filaria perstans and 

 Filaria diurna is based more upon analogy thau fact and that this 



