LABORATORY METHODS IN .MALARIA 375 



Specimens may be mounted fresh or first fixed by formalin or 

 other fixative. Schandinn's fixative is apt to make the unstained 

 specimens too opaque. 



It is usually unnecessary to prepare a cell beforehand for en- 

 closing such small objects as stomachs or salivary glands of mos- 

 quitoes. Sometimes it is advisable to place a bit of thin cover- 

 glass or some small object with the specimen to prevent too much 

 flattening by the coverglass. If the specimen is first attached to 

 the slide by some fixative it becomes easier to mount it. The speci- 

 mens should be mounted free from air bubbles. The excess of 

 fluid should be removed from the preparation, and the slide at the 

 edge of the coverglass well dried before applying the cement. I 

 usually make the first ring of asphalt cement or of a cement of 

 similar consistency. When this has dried I superimpose a second 

 ring of soft paraflin. This is conveniently made by melting to- 

 gether equal parts of paraflin and liquid petrolatum (Liquid 

 Petrolatum Heavy U.S. P. IX) and should be liquefied by heat and 

 applied when quite warm. A ring of some firmer cement may then 

 be added as a protection to the paraffin ring. 



I have devised a method of making permanent preparations of 

 unstained material, easily carried out and very serviceable for the 

 examination of specimens under low magnification. Take up the 

 stomach or salivary glands in a small pipette and place them in 

 a minimum of fluid at the side of a clear glass vial about forty 

 millimeters long and five millimeters in diameter. The thinner the 

 wall of the vial the better. It should be well cleaned before use. 

 The excess fluid may be drawn away by means of a pipette or a 

 narrow strip of filter paper inserted in the vial ; and the specimen 

 may be arranged under the lens by means of a bent dissecting 

 needle. Place in the mouth of the vial a cotton plug moistened with 

 a forty per cent solution of formalin or other vapor fixative. Place 

 the vial mouth downward. The vapor will fix the specimen to the 

 side of the vial as the fluid drains into the cotton plug. The vial 

 may then be filled with dilute formalin or any preserving fluid 

 desired, and tightly stoppered with a rubber or other impermeable 

 stopper, taking care to avoid the inclusion of air bubbles. 



To examine the specimen microscopically, fasten the vial tem- 

 porarily to a slide with a strip of adhesive tape and examine under 

 any objective with sufficient working distance to focus through 

 the wall of the vial. The image appears much more distinctly if 



