xhi, b, i Barber: The Transmission of Malaria 37 



ordinary dinner plates filled with wet sand or merely partly 

 filled with water. The wooden sides of the sieves keep moist, 

 and further moisture can be secured by allowing a flap of the 

 covering to dip into the water or by placing wet pieces of filter 

 paper on the top. The cages in most of these experiments were 

 placed in a meat safe, which was kept in the laboratory and 

 carefully protected from ants. 



No food is necessary if the mosquitoes are to be dissected 

 within a few days. In the case of mosquitoes kept for longer 

 periods, I have followed the method of Darling by feeding with a 

 pinch of white sugar placed on moist filter paper in contact 

 with the top of the cage. The proportion of mosquitoes thus 

 fed that became infected with yeasts or bacteria was much 

 smaller than among those fed on fruit juices of any kind. 



For dissection the mosquitoes were removed from the cage 

 singly by means of test tubes. The test tubes, each containing 

 a single mosquito, were plugged and placed in a rack on the 

 table convenient to the microscope. Each specimen was chloro- 

 formed immediately before dissection. Where positives were 

 found in the first ones examined, the remainder were sometimes 

 returned to the cage and reserved for dissection after the par- 

 asites had further matured. 



The chloroformed mosquito may be spilled from the test tube 

 directly on a slide and dissected immediately or after a prelimi- 

 nary examination under the low power of a compound micros- 

 cope. Very fine sewing needles, ground to a blade at the tip 

 and fixed in a stick, make convenient dissecting needles when 

 nothing else is at hand. Very shallow drops of salt solution are 

 most convenient in dissection. In order to prevent the rounding 

 of the drops, I have used slides carefully cleaned in the ordinary 

 way, and I have not found it necessary to use slides prepared 

 with bile. After the gut is drawn out, I have found it con- 

 venient to remove the excess of liquid with a bit of filter paper 

 cleanly cut at the margins. This may be manipulated with the 

 needles under the dissecting lens. The drop is thus rendered 

 very shallow, and the malpighian tubes once drawn back re- 

 main in position. More liquid may be added, if necessary, 

 after the cover glass has been adjusted. If the last segment of 

 the abdomen is left on the gut, this will not be crushed too flat 

 by the cover glass. If one wishes to flatten the gut further, one 

 has only to press down the cover with a needle. 



With an assistant to chloroform the mosquitoes and keep a 

 slide ready prepared for use, one can dissect rapidly. The dis- 

 section itself and the subsequent examination of the gut salivary 



