LABORATORY METHODS IN MALARIA 371 



In case the head has been removed for dissection of the saHvary 

 glands, it is possible to draw out the midgut without removing 

 the abdomen from the thorax ; but it is usually best to remove the 

 abdomen in order to draw out the stomach more easily. If the 

 hindgut breaks during traction, it is almost always possible to 

 pull out the stomach from the anterior end of the abdomen with- 

 out injuring it. 



When the probabilities of finding an infected stomach are small, 

 as is usually the case when mosquitoes caught in the wild state are 

 examined to determine natural infection, much time can be saved 

 in both dissection and examination by dissecting three or more 

 specimens in the same drop of salt solution, and covering the 

 stomachs with one coverglass. If a positive specimen appears, it 

 may be separated from the others. 



\'ery serviceable dissecting needles may be made by inserting 

 large sewing needles (No. 10) in a stick or in a special holder. 

 The points may be easily ground into the form of small blades. 

 Small thin covers are preferable for mounting stomachs. I pre- 

 fer for the examination of single stomachs a square cover, about 

 five millimeters square and Xo. i in thickness. It is possible to 

 use fragments of large covers, but it is far better to order special 

 sizes from the dealers. 



A binocular or other dissecting microscope may be employed. 

 Since only a small magnification (six or seven diameters) is needed 

 for dissection, a simple lens mounted in a lens-holder will serve. 

 I have found a simple lens, held in a lens-holder provided with 

 ratchet and pinion and a long movable arm, a very convenient 

 apparatus, since it is portable and allows abundant working room. 

 A thick board or an ordinary wooden slide box will serve as a 

 stage, a portion of which is blackened to afford a dark back- 

 ground for dissection. A small fine whetstone, fastened to the side 

 of the stage with its upper surface flush with the surface of the 

 stage, has proved very convenient for cleaning or sharpening 

 needles under the lens. 



Identification of oocysts. Oocysts are more or less spherical in 

 form and contain denser protoplasm than do gut cells. They are 

 attached to the stomach wall and can often be distinguished by 

 their position from stomach cells, yeast cells or other bodies which 

 lie within the stomach. A characteristic very useful for identifica- 

 tion of oocysts is the pigment, which is easily found in oocysts 



