724 PROTOZOOLOGY 



warmed to 50°C. The fixative is placed in a square Petri dish and the 

 smear is gently dropped on it with the smeared surface facing down- 

 ward. With a little experience, air bubbles can be avoided and make 

 the smear float on the surface of the fixative. After about one minute, 

 turn it around and let it stay on the bottom of the dish for 5 to 10 

 more minutes. In case the smear is too thick, a thin coat of vaseline 

 on the upper side of the coverglass will make it to float. About six 

 coverglass-smears may be fixed in the dish simultaneously. 



The coverglass-smears are now transferred to a Columbia staining 

 jar for coverglasses, containing 50% alcohol for 10 minutes, followed 

 by two changes for similar length of time. Transfer the smears next 

 to 30% alcohol for 5 minutes, and then to a jar with water, which 

 is now placed under gently running tap water for 15 minutes. Rinse 

 them in distilled water and stain. 



Other fixatives frequently used for Protozoa are as follows: 



Bouin's fluid 



Picric acid (saturated) 75 cc. 



Formaldehyde 25 cc. 



Glacial acetic acid 5 cc. 



Fixation for 5-30 minutes; wash with 70% alcohol until picric acid 

 is completely washed away from the smears. 

 Sublimate-acetic 



Saturated sublimate solution 100 cc. 



Glacial acetic acid 2 cc. 



This is the original fixative for Feulgen's nucleal reaction (p. 726). 

 Fixation and after-treatment similar to Schaudinn's fluid. 



Carney's fluid 

 Absolute alcohol 30 cc. 



Glacial acetic acid 10 cc. 



Fixation for 5-30 minutes; wash in 95% alcohol. 

 Osmium tetroxide 



The vapor from or the solution itself of 1% Osmium tetroxide may 



be used. Fixation in 2-5 minutes; wash in running water. 



Flemming's fluid 



1% chromic acid 30 cc. 



2% osmium tetroxide 8 cc. 



Glacial acetic acid 2 cc. 



