OF filauta sanguinis nOMTNIS. 



307 



to know the plan I found most successful in procuring Filaria- 

 beariug mosquitos, and how their bodies were afterwards treated 

 for microscopic observation. Such details may appear frivolous 

 and unimportant ; but by following them the observer will be 

 spared disappointment, and economize his time and patience. 



I persuaded a Chinaman, in whose blood I had already ascer- 

 tained that FilaricB abounded, to sleep in what is known as a 

 mosquito -house, in a room where mosquitos were plentiful. 

 After he had gone to bed a light was placed beside him, and the 

 door of the mosquito-house kept open for half an hour. In this 

 way many mosquitos entered the "house;" the ligbt was then 

 put out, and the door closed. Next morning the walls of the 

 " house " were covered with an abundant supply of insects with 

 abdomens thoroughly distended. They were then caught below 

 a w^ineglass, paralyzed by means of a whiff of tobacco -smoke, and 

 transferred to small phials, into some of which a little water had 

 been poured. A cover providing for ventilation was then placed 

 over the mouth of the phial. The effect of the tobacco-smoke, if 

 it has not been applied too long, is very evanescent, and seems to 

 have no prejudicial influence on the posture of the mosquito. 

 From the phials they may be removed from time to time, as re- 

 quired, by again paralyzing with tobacco and seizing them by the 

 thorax with a fine pincers. The abdomen is then torn off, placed 

 on a glass slide, and a small cylinder, such as a thin penholder, 

 rolled over it from the anus towards the severed thoracic attach- 

 ment. In this way the contents are safely and efficiently ex- 

 pressed, and observation is not interfered with by the almost 

 opaque integument. If the contents are white and dry a little 

 water should be added and mixed carefully with the mass, so as 

 to allow of the easy separation of the two large ovisacs. These 

 can be removed in this way by the needle, and transferred to 

 another slide for separate examination. A thin covering-glass 

 should be placed over the residue, which will be found to contain 

 the Filar ice either within the walls of the stomach, or, if these have 

 been ruptured by too rough manipulation, floating in the sur- 

 rounding water. 



Large proportion of FilarisB ingested hy the Mosquito. — The 

 blood in the stomach of a mosquito that has fed on a Filaria-mh%icdi 

 man usually contains a much larger proportion of FilaricB than 

 does an equal quantity of blood obtained from the same man in 

 the usual way by pricking the finger. Thus six small slides, 



LINN. JOUEN. — ZOOLOGY, VOL. XIY, 22 



