892 PROTOZOOLOGY 



Physiological salt solution. Widely used concentrations of NaCl 

 solutions are 0.5-0.7% for cold-blooded animals and 0.8-0.9% for 

 warm-blooded animals. 



Ringer's solution. The one Dobell advocated has been given al- 

 ready (p. 887). Another frequently used solution consists of 



NaCl 0.8 gm. 



KC1 0.02 gm. 



CaCl 2 0.02 gm. 



(NaHC0 3 0.02 gm.) 

 Glass distilled water 100 cc. 



For demonstrating organellae, the following reagents which kill 

 the Protozoa upon application, may be used on living Protozoa. 



LugoFs solution. This is made up of potassium iodide 1.5 gm., 

 water 25 cc, and iodine 1 gm. The solution deteriorates easily. 

 Flagella and cilia stain clearly. Glycogen bodies stain ordinarily red- 

 dish brown. Cysts of intestinal Protozoa are more easily studied in 

 Lugol's solution. 



Sudan III and IV. 2% absolute alcohol solution diluted before use 

 with the same amount of 45% alcohol. Neutral fats are stained red. 



Methyl green. 1% solution in 1% acetic acid solution makes an 

 excellent nuclear stain. 



Nigrosin. 10% solution if used in smears and air-dried makes the 

 pellicular patterns of flagellates and ciliates stand out clearly. 



In the case of faecal examination if the stool is dysenteric, a small 

 portion is placed by a tooth-pick or platinum loop on a slide and 

 covered with a cover glass. Before placing the cover, all large parti- 

 cles must be removed quickly so that the smear will be uniformly 

 thin. Smears of diarrhoeic stools can be made in a similar way. But 

 if the faecal material is formed or semiformed, a small drop of warm 

 (37°C.) 0.85% NaCl solution is first placed on the slide, and a small 

 portion of the faeces, particularly mucus, pus or blood, is emulsified 

 in it. The whole is covered by a coverglass. The faecal smear should 

 not be too thick or too thin for a satisfactory observation. If the 

 smear is too thick, it will be impossible to distinguish objects 

 clearly, and on the other hand, if it is too thin, there will be much 

 time lost in observing widely scattered Protozoa. The optimum 

 thickness of the smear is one through which the print of this page 

 can be read. 



The success in faecal examination for intestinal Protozoa depends 

 almost entirely on continued practice, since the faecal matter con- 

 tains myriads of objects which may resemble Protozoa (Fig. 375, 



