46 PARASITIC AMGEBJE OF MAN. 



Cover glass preparations may be fixed either wet 

 or dry. If one desires to study the minute morphology 

 of amoebae it is best to fix the preparations wet, 

 although carefully prepared dry specimens often give 

 good results, and the writer has found that dry prep- 

 arations are just as useful for ordinary work. If the 

 specimens are to be fixed wet the following procedure 

 is to be recommended: 



The stool containing the amoeba? is spread in as 

 even and thin a layer as possible upon the cover 

 glass, which is then placed with the material down- 

 wards in a dish containing the fixing solution. While 

 some of the material will dissolve in the solution, it 

 will be found that most of the amoebae are retained 

 upon the cover glass. After fixing, the preparations 

 are rinsed in alcohol (50 per cent.) and hardened 

 with 70 or 80 per cent, alcohol. 



A quick and efficient method of wet fixation is by 

 exposure to osmic acid vapor, the osmic acid solution 

 already described being used for this purpose. This 

 method is most useful if Giemsa's or Wright's stain- 

 ing methods are used and it is desired to avoid artificial 

 changes in the structure of the amoebae. The technique 

 of fixation by this method is as follows : 



A cell, slightly smaller in diameter than the cover 

 glass containing the material to be examined, and 

 from one-half to three-quarters of an inch deep, is 



