The metamorphosis of Filaria sanguinis hominis in the mosquito / By Patrick Manson.

  • Manson, Patrick, Sir, 1844-1922.
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: The metamorphosis of Filaria sanguinis hominis in the mosquito / By Patrick Manson. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

    12/76 (page 370)
    engaged a man in whose blood the Filaria abounded. A large square wooden frame (10 ft. xlO ft. X6^ ft.) covered with mosquito-netting and provided with a door was erected in a room where mosquitoes abounded. Under this mosquito-house the man slept, the door of the house being closed some hours after he had gone to bed. Next morning the mosquitoes that had entered by the door, and preyed on the man's blood, were found clinging to the inside of the netting, their abdomens distended with blood. These my servant captured under a wine-glass, and after paralyzing them with a whiff of tobacco smoke transferred them each to a dry phial covered with gauze. When the insects had recovered from the effect of the tobacco and ascended the side of the bottle for a little distance, a small quantity of water was introduced through a pipette. Latterly I employed large-mouthed stoppered bottles, holding about two ounces, instead of the phials. Tobacco could in this way be dispensed with, and a considerable mortality avoided. The bottles were dated and put under a dark shade. When the weather became cool I got better results by placing the bottles in an incubator, where the insects were kept in a damp atmosphere at a temperature ranging from 80° to 85° Pahr. In this way I endeavoured to imitate nature. Every morning during many weeks a fresh crop of Filaria-ch&rged mosquitoes was gathered. Tor the purposes of this investigation quite a thousand insects had to be provided. From time to time, as required, they were removed from the bottles after being killed by chloroform. The legs and wings and head were torn off. The thorax was then separated from the abdomen, each being placed on a separate slide. In the case of the abdomen the contents were expressed by rolliug a penholder from the free to the severed thoracic end; a cover-glass was then placed on the expressed blood. If necessary, a little water or sulphate of soda solution (sp. gr. 1050) was used to soften the blood and allow of the easy removal of the two large ovisacs, which, when crushed, obscure the slide very much. The thorax is best treated by being broken up, and teased out with a couple of sharp needles in a droplet of water, before the cover-glass is applied. Thus prepared, an inch objective readily detects the parasites among the tissues of the insect. To preserve the Filaria thus displayed the cover-glass must be carefully lifted up, and what remains on the slide allowed to dry, the large pieces of mosquito debris being first picked off with a fine forceps. After drying for a day or, better, two, it may be stained with an aniline dye (gentian violet answers very well), and after washing and redrying mounted in Canada balsam. In the case of Filaria in the blood from the abdomen of the mosquito it is only necessary to dry the preparation before mounting in balsam. The red colour of the blood gives sufficient contrast to display, at all events, the outline of the parasites. Whenever practicable, fresh and unstained preparations should be examined ; for while stained specimens show the outline well enough, they are useless in studying the details of internal structure. My mosquito-house and filarious patient were visited by three species of mosquito, perhaps four. All of these were capable of imbibing the Filaria, but only one of them is, I believe, capable of conducting the metamorphosis to a successful conclusion. Both of the impotent species are of the kind known as tiger mosquitoes, i. e. their bodies and legs are banded, or flecked with white. One is quite a large insect, half an inch in length, with numerous sooty, easily detached scales; the eggs of this species when