MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



Technique: 



Used in the same way as the strong solution {see above), except 

 that the volume of the fixative required is about eight or ten times 

 that of the material to be fixed. 



Remarks: 



See under Flemming's Fluid (strong). 



Formalin Neutral 



Recommended for : 



Animal tissues in general, particularly nervous tissue. 



Formula: 



Formalin (formaldehyde 40%) . . 100 ml. 



Tap water . . . . . . . . 900 ml. 



Magnesium carbonate . . . . to excess 



Shake well and allow to stand several hours at least; then 

 decant off the volume of the clear fluid required for fixation. 



Technique: 



Fix at least twenty-four hours at room temperature, or six to 

 eight hours at 50-60° C. Washing out is unnecessary. 



Remarks: 



Formalin penetrates well, tissues may be kept in it for long 

 periods without undue hardening, although there is a gradual 

 decrease in basophilia of cytoplasm and nuclei, and certain cyto- 

 plasmic structures are not hardened by it sufficiently to permit 

 paraffin embedding. Best adapted to material which is to be em- 

 bedded in celloidin rather than in paraffin wax; also suitable for 

 frozen sections. 



Formalin Buffered 



Formula: 



Neutral formalin, as above . . . . i litre 



Sodium dihydrogen phosphate, mono- 

 hydrate, A.R. . . . . • • 4 gni. 

 Disodium phosphate anhydrous, A.R. 6-5 gm. 



Technique: 

 As for neutral formalin. 



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