48 PARASITIC AMCEB^ OF MAN. 



may be decolorized in 70 per cent, alcohol contain- 

 ing a few drops of hydrochloric acid, the process 

 being watched under the microscope until the para- 

 sites appear a pale bluish black. They are then placed 

 in a solution consisting of 1 drop of ammonia to 100 

 c.c. of 70 per cent, alcohol until the color turns blue, 

 when they are rinsed in 70 per cent, alcohol and 

 mounted. If desired, the cytoplasm of the amoeba? 

 may be stained by eosin after they have been stained 

 with hgematoxylin which, of course, only colors the 

 nucleus. 



If carbol-f uchsin, methylene blue, or gentian violet 

 is used for staining, the fixed preparations are placed 

 in the staining solution for a few moments, washed 

 in 70 per cent, alcohol, and mounted. These stains 

 are of very little service in the study of these para- 

 sites. 



The Iron Hcematoocylin Method of Heidenhcdn. 

 This is a most valuable method for studying struc- 

 tural details. If it is used the specimens must be 

 fixed wet with alcoholic solution of mercuric chloride 

 or with osmic acid vapor. The following solutions 

 are used in this method: 



1. A 2.5 per cent, watery solution of iron-alum 

 (Ferrous ammonium sulphate). 



2. A 0.5 to 1 per cent, watery solution of 

 hsematoxylin, which should be at least four weeks old. 



