MALARIA 1 89 



then be stained blue. Carbol thionin is even more suitable, 

 as the colour which it imparts to the nuclei of the leucocytes 

 is not deep and the red corpuscles are merely tinged. This is 

 the stain which we recommend for general use, and in cases 

 in which the nature of the organism (if one be presented) is 

 entirely unknown. 



If bacteria are detected by any of these methods their nature 

 must be recognized by a consideration of their morphological 

 features and staining reactions. 



MALARIA 



The blood in a suspected case of malaria may be examined 

 fresh or in stained films. Of these methods the former is the 

 better, and should be used if possible. An examination of 



FIG. 31. MALARIAL PARASITES IN THE BLOOD (see also Plate XI.). 

 The dark area shows the parasite as it appears when stained with thionin. 



stained specimens should also be made, and is convenient, as it 

 can be performed away from the patient and at leisure. 



Fresh films are made by touching' a drop of blood on the 

 patient's ear with the centre of a perfectly clean cover-glass, 

 so as to remove an extremely small quantity of blood. This 

 cover-glass is then allowed to fall on to a clean slide, so that 

 the droplet of blood may be spread out by capillary attraction 

 and by the weight of the cover-glass, just as is the case in the 

 method of making blood-films, to be described subsequently. 

 But the slide is not separated from the cover-glass; they are 

 examined just as they are, a ring of vaseline being painted 

 round the edge of the cover-glass to prevent evaporation. 



The specimen is examined with a J-inch objective, and a 

 place found in which the corpuscles are spread in a single 

 layer; this part is then searched thoroughly with a T V-inch oil- 



