370 DE. P. MANSON ON THE METAMOEPHOSIS OP 



engaged a man in whose blood the Filaria abounded. A large square wooden frame 

 (10 ft. x 10 ft. x Gh 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 bad 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 

 1 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° Eahr. In 

 this way I endeavoured to imitate nature. Every morning during many weeks a fresh 

 crop of Filaria-chargeA mosquitoes was gathered. Eor 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 Filarice 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 



