36 PROTOZOAN PARASITISM 



Shorter methods of stainmg may be used, such as 

 Mayer's ''Haemalum," but the details are not as 

 well presented as in the iron-haematoxylon. 



Mayer's Haemalum may be made by dissolving 1 

 gram of haematoxylon crystals in 1000 cc. of dis- 

 tilled water and adding 50 grams of potash alum and 

 0.2 gram of sodium iodate. 



The fixed and washed slide preparations from the 

 fourth step in the technique given above for the 

 iron-haematoxylon method should be placed in this 

 stain for 15-20 minutes. The slides are then washed 

 in tap water until blue in color, with the water run- 

 ning or being frequently changed. The preparations 

 are dehydrated, cleared and mounted as above. 



The iron-haematoxylon staining is best for care- 

 ful study of nuclear and other structural detail. 

 Mayer's Haemalum is much shorter and less difficult 

 and is sufficient for identifying the organisms. 



Study of fresh unstained materials for the active 

 amoebae is only a preliminary step in the identifica- 

 tion of the organisms. In the hands of an experi- 

 enced protozoologist it may be conclusive in the 

 majority of instances but it is reasonably certain that 

 even the expert will err at times. Study of prepara- 

 tions stained by the iron-haematoxylon method will 

 usually lead to accurate identification in the vegeta- 

 tive phase by the expert protozoologist. These 

 measures, however, are not to be depended upon in 

 less expert hands. The amoebae are frequently in 

 such active form as to render unreliable an opinion as 



