464 RESEARCH IN PROTOZOOLOGY 



smear should be such that it is just possible to read newspaper 

 print through it. It is advisable, particularly when examining in- 

 testinal amoebae, to provide for maintaining the specimen at 37° C. 

 or thereabouts by the use of a warm chamber to enclose the micro- 

 scope or a warm stage. If either of these two items of apparatus are 

 not available, the temperature of the slide may be kept at a satisfac- 

 tory height by placing heated coins upon it. 



Fresh blood is simply diluted with an isotonic fluid such as 

 physiological saline,^ Ringer's,^ or Locke's * solution to the point 

 where the organisms present will not be obscured by the concen- 

 tration of red blood cells. A drop of the diluted blood is placed 

 upon a clean slide and covered with a clean coverslip. 



Observation with the darkfield microscope is useful in counting 

 flagella, observing ciliation, etc. Material to be examined must be 

 as nearly free as possible from other small particles such as bac- 

 teria to reduce "flashing." Rapidly moving protozoa may be im- 

 mobilized by holding the uncovered smear face downward over a 

 bottle of ten per cent acetic acid for one minute. 



Concentration Methods. Various concentration methods have 

 been devised for the purposes of ( i ) facilitating the diagnosis of 

 infections with intestinal amoebae, flagellates, or coccidia, or (2) of 

 providing a sufficient quantity of comparatively rare material for 

 study or inoculation. These methods are applicable only to cyst- 

 producing organisms, as the measures involved are, as a rule, too 

 vigorous to permit the survival of anything but cysts. 



^ Physio log ical salin e 



Sodium chloride 8.5 gms. 



Distilled water looo.o c.c. 



'Ringer's solution 



Sodium chloride 8.00 gms. 



Calcium chloride (anhydrous) 0.20 gm. 



Potassium chloride 0.20 gm. 



Sodium bicarbonate 0.20 gm. 



Dextrose (may be omitted) i.oo gm. 



Distilled water 1000. go c.c. 



* Locke's solution 



Sodium chloride 9.00 gms. 



Calcium chloride (anhydrous) 0.24 gm. 



Potassium chloride 0.42 gm. 



Potassium bicarbonate 0.20 gm. 



Dextrose (may be omitted) i.oo to 2.50 gms. 



Distilled water 1000.00 c.c. 



