xin, D. 5 Haughwout: Protozoa of Manila and Vicinity: I 187 



balsam. The process of staining and differentiation should be 

 carefully watched under the microscope in order that the re- 

 quired structural details may be clearly brought out. Some 

 experience will be necessary to get good results, but if the begin- 

 ner will observe and profit by his mistakes, he will soon be able 

 to make passably good preparations. 



In the case of blood parasites such as trypanosomes, malarial 

 parasites, Babesia, and the like regular blood films should be 

 made on a perfectly clean, grease-free slide. The films should 

 be spread so as to avoid crushing the blood elements and the 

 parasites. They should be quickly dried and then fixed for five 

 minutes in absolute methyl alcohol. They may be then stained 

 with Giemsa's solution. I believe that this is the best blood stain 

 we have, but in its absence one may use Wright's, Hastings's, 

 Jenner's, or any of the other standard formulae. I carry out 

 the process of staining with Giemsa's solution in shallow Petri 

 dishes just large enough to hold the slides. The slides are 

 supported, face down, on each end by a thin piece of glass, and 

 the staining solution is run in between the bottom of the dish 

 and the smeared surface of the slide with a pipette. By using 

 this method the precipitations that tend to form from the blood 

 stains will fall on the surface of the dish instead of being depos- 

 ited on the slide to perplex the microscopist. 



The Giemsa solution should be made up in distilled water, 

 using one drop of the stock staining solution to each cubic centi- 

 meter of distilled water. Experience will show how long to stain 

 the preparation. Five or six minutes will generally answer for 

 trypanosomes, if the film be fresh. Fifteen minutes or even 

 longer are required for intracorpuscular parasites. When the 

 slide is stained, wash it quickly in a stream of distilled water, 

 blot lightly with filter paper, and lean the slide up, face inward, 

 until it is thoroughly dry. The preparation may be then mounted 

 in Canada balsam, or it may be examined directly under the 

 oil-immersion objective. 



When protozoa are scarce in a culture, or it is desired to collect 

 small surface-dwelling forms, cover glasses may be floated on the 

 surface of the culture overnight and then transferred, face up, 

 to a Syracuse watch glass containing fixing fluid. The process 

 of staining, differentiation, dehydrating, and so forth may be 

 carried on under the microscope in the Syracuse dishes in the 

 same way that the slides were handled in the staining jars. 



Individual protozoa of the larger species may be picked out of 

 a watch glass containing them, with a capillary pipette, the oper- 

 ator working under a binocular microscope or Hastings's lens. 



