SECTION THREE 



Recipe : 



Potass, dichromate 3% aqueous . . 35 ml. 

 Chromium trioxide i % aqueous . . 35 ml. 

 Osmic acid 2% . . . . . . 20 ml. 



Techfiique: 



Fix for six to twenty-four hours ; then wash in running water 

 for the same length of time. 



Mix A and B immediately before use. 



Technique: 



Fix for one to twenty-four hours according to the material ; for 

 chromosomes an hour is sufficient. Wash with running water for 

 twenty-four hours. 



Remarks: 



The penetration power of this fixative is poor ; and that of the 

 weak solution {see below) is poorer still ; however, either solution 

 gives good results with basic stains, particularly safranin, and iron 

 haematoxylin. Quite apart from their high cost, Flemming fixa- 

 tives should definitely not be employed as general fixatives, but 

 only in special cases for very small pieces of tissue where fixation 

 extending through a layer of about four or five cells in thickness is 

 sufficient, as this is the limit of their penetrating power even in 

 loose-celled tissues. 



Q* 



477 



