OF FILARIA SANGUINIS HOMTNIS. 



305 



intestinal canal, the Lumhricus and thread-worm ; the latter is 

 followed by the several species of tapeworm, and also by other 

 kinds of Entozoa. 



I find that in cases where embryo Filar ice are not in great 

 abundance in the blood, we may infer that there are only one or 

 two parent worms ; they often disappear completely for a time, to 

 reappear after the lapse of a few days or weeks. From this cir- 

 cumstance I infer — 1st, that reproduction is of an intermitting 

 and not of a continuous character ; and, 2ndly, that the embryos, 

 after a certain time, are either disintegrated in the blood or are 

 voided in the excretions. The latter does occur, I know from 

 personal investigation, in the urine ; and we have Dr. Lewis's 

 testimony that he has found the animals in the tears. In this 

 way they may have an opportunity of continuing development 

 either free (as in the case of the Lumhricus) in the media into 

 which the excretions are voided, or in the body of another animal 

 which has intentionally or accidentally fed on these (as in the 

 case of the tapeworms). Man, in his turn, may then swallow this 

 hypothetic animal or other thing containing the embryo suitably 

 perfected, and so complete the circle. This is the history of many 

 Entozoa ; but I have evidence to adduce that, if it be one way in 

 which F. sanguinis hominis is nursed, it is not the only way, and 

 therefore probably not the way at all. 



The Mosquito found to he tlie Nurse. — It occurred to me that, as 

 the first step in the history of the hsematozoon was in the blood, 

 the next might happen in an animal who fed on that fluid. To 

 test this idea I procured mosquitos that had fed on the patient 

 Hinlo's blood (Case No. 46, published in ' Med. Times & Gaz.' 

 for March), and, examining the expressed contents of their 

 abdomens from day to day with the microscope, I found that my 

 idea was correct, and that the hsematozoon which entered the 

 mosquito as a simple structureless animal, left it, after passing 

 through a series of highly interesting metamorphoses, much 

 increased in size, possessing an alimentary canal, and being other- 

 wise suited for an independent existence. 



History of the Mosquito after feeding on Hvma/n blood. — I may 

 mention that my observations have been made exclusively on 

 the females of one species of mosquito. I have never, in many 

 hundreds of specimens, met with a male insect charged with blood. 

 This is explained by the arrangement of the appendages and pro- 

 boscis of the male mosquito, which prevents it from penetrating 



