FILARIA SANGUINIS HOMINIS IN THE MOSQUITO. 383 



canal and other organs, and enhanced muscular power ; then eat or bore its way through 

 the integuments of the dying mosquito, and finally obtain liberty in the water into which 

 the insect has fallen. It is impossible to do this ; but, by comparison of a large number 

 of dissections, we can follow the history of the animal in the mosquito almost as perfectly 

 as if we had watched in transparent tissues the progress of a single individual from the 

 human body to the water. 



The experimentum cruris of this theory, as I have already said, I have not had the 

 hardihood to attempt. But from what I have written, any one anxious to make it will 

 have no difficulty in gathering what is likely to be the most successful method. Were I 

 to attempt it I would proceed in this fashion : — I would feed my mosquitoes on a filarious 

 subject, I would collect them every morning, giving each a bottle to itself. Those that 

 survived to the afternoon of the seventh day I would transfer to test-tubes ; these I would 

 invert over a watch-glass, containing a little water. When the insect died I would allow 

 it to remain on the water a few hours and then remove it. The water it had fallen into, 

 and which probably now contains the Filar ia, I would transfer to a stock-bottle contain- 

 ing water. This process I would repeat for several days. I would then administer 

 portions of the contents of the stock-bottle to the subject of the experiment. I would 

 continue this for a month, every day adding fresh mosquito-water to the stock-bottle, 

 and every day administering a draught of its contents. After a time I would commence 

 the examination at night of the finger-blood. I am quite satisfied as to what would be 

 the result. 



EXPLANATION OF PLATE XXXIX. 



[All the figures with the exception of figs. 10, 34, 35, 37, 43, 44, 45, and 46, are magnified about 



188 diameters.] 



Fig. 1. The embryo Filaria sanguinis hominis as it appears in the blood, or lymph, or in the abdomen of 

 the mosquito immediately after ingestion, ^V" x xobo"- 



Fig. 2. A Filaria about an hour after ingestion by the mosquito. The sheath has been cast, transverse 

 striation and oval pouting are very distinct, and the animal is indulging in the snake-like 

 wriggling by which it moves from the abdomen to the thoracic viscera. In the mosquito from 

 which this specimen was obtained many Filaria were found in the newly ingested blood in the 

 insect's abdomen. All were active and transversely striated. Most had cast the sheath. In 

 one the sheath was lying at some distance, in another it trailed after the animal, while in a 

 third it lay across it. Oral pouting was distinct in all ; but no double outline, or further struc- 

 ture, could be detected in any of them. In the same insect two Filaria were found in the 

 thorax ; they were structureless, without sheath, somewhat swollen from endosmosis, an obscure 

 convoluted granular-looking condensation occupying most of the body. 



Fig. 3. From the thorax twelve hours after ingestion, y^/x g l oo" - 



The abdomen of the insect was half filled with blood, in which moved many active, trans- 

 versely striated, pouting Filaria. They had no sheath. In the thorax many were found. 



SECOND SERIES. — ZOOLOGY, VOL. II. 56 



