MALARIA. 383 



large. The blood-cells must lie side by side somewhat 

 scattered, as arrangement in rouleaux would conceal the 

 parasites. The preparation is then examined with a good 

 oil-immersion lens. If the examination is to be continued 

 for some time, evaporation is prevented by surrounding the 

 margin of the cover-slip with wax, or the uniformly dis- 

 tributed drop of blood is examined on an excavated slide, 

 at the bottom of which is a drop of water. To stimulate 

 ameboid movement, a warm stage should be employed. 

 Examination in a warm room is possible, however, for an 

 hour or more, without the aid of this device. 



In the preparation of dry specimens also it is important to 

 obtain quite a small drop of blood. The cover-slip is then 

 quickly drawn over the surface of a second cover-slip, and 

 both, protected from dust, are permitted to dry in the air. 

 The dried preparations are placed for fixation for from 

 five to thirty minutes in a mixture of equal parts of abso- 

 lute alcohol and ether. They are now dried between lay- 

 ers of bibulous paper, and are stained either in dilute 

 aqueous solution of methylene-b'lue, and then, after rinsing 

 with water, in two per cent, alcoholic (sixty per cent.) solu- 

 tion of eosin ; or the specimen is exposed to the action of 

 both stains at the same time. For this purpose Plehn 

 recommends the following mixture : 



Concentrated aqueous solution of methylene- 

 blue, 60 



One-half per cent, solution of eosin (in sev- 

 enty-five per cent, alcohol), 20 



Distilled water, 40. 



The preparation is kept in this solution for from five to 

 ten minutes, and is then rinsed in water, dried, and examined 

 in xylol Canada balsam. The hemoglobin-containing blood- 

 cells are thereby stained red ; the plasmic body of the para- 

 sites, more or less deeply blue. For -rapid examination, 

 simple treatment with aqueous methylene-blue suffices. 

 For special examinations and for the determination of the 

 finer structural relations, a large number of methods of 

 fixation and staining have been proposed. For diagnostic 

 purposes, examination of fresh specimens and of stained 

 preparations by the method described is quite sufficient. 



With regard to the diagnostic utility of the results of 

 the examination, the following statements may be made : 



