staining, practical and theoretical 

 Rapid Method for Staining Fats 



Solutions required: 



A. Sodium chloride A.R. grade 0-9% 



in distilled water . . . . 95 ml. 



Formalin . . . . . . • • 5 nil- 



B. Sudan Black B, saturated in 70% 



alcohol (this should be freshly 

 filtered). 



Note: Ethylene or Propylene Glycol may be em- 

 ployed as the solvent (see page 428). 



C. Apathy's mountant. 



Technique: 



1. Thin slices of tissue are fixed for ten minutes at 37-40° C. in 

 Solution A. 



2. Transfer the material directly from the fixative to the freezing 

 microtome and cut sections about 5// in thickness. 



3. By means of a camel-hair brush, moistened with 50% alcohol, 

 transfer sections from the microtome knife directly to the first of a 

 series of dishes previously arranged as follows, in order of their 

 use : 70% alcohol, Sudan Black solution (as above), 50% alcohol ; 

 distilled water. 



4. After immersion in 70% alcohol (in the first dish) for two 

 minutes, stain in the Sudan Black for ten minutes, or longer if 

 time permits. 



5. Rinse in the 50% alcohol. 



6. Transfer to the distilled water : mount in Apathy's medium, 

 or, if there is sufficient time, counterstain for about three minutes 

 in Carmalum ; then rinse in distilled water before mounting. 



Results: 



Neutral fat and myelin : blue-black to black; nuclei: red. 



GELATINE EMBEDDING 



This method of embedding is employed when sections of loose 

 friable tissues are required. Dehydration is entirely eliminated 

 since the embedding takes place directly from water. The gela- 

 tine which is retained during the staining processes holds the 

 tissues together without absorbing the stain itself. 



492 



