STAINING, PRACTICAL AND THEORETICAL 



Flemming's Solution (weak) 

 Recommended for: 



All purposes for which Flemming's strong solution is used. 



Recipe : 



A. Chromic acid I % .. ..• 25 ml. 

 Acetic acid 1% 10 ml. 



B. Osmic acid 1% . . . . . . 10 ml. 



Distilled water . , . . . . 50 ml. 



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 neurological tissue. 



Formula: 



FormaUn (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. For this reason the proportion of formalin 

 (formaldehyde 40%) to water is often increased to i : 3. 



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