Appendix B: Some Standard Reagents and Their Uses 163 



5. Bichromate of Potassium and Acetic Acid ( Telly esnicky's 



fluid). - 



Bichromate of potassium ....... 3 grams 



Glacial acetic acid 5 c.c. 



Water 100 c.c. 



It is best not to add the acetic acid until just before using. 

 This is a good general reagent. It is valuable for embryos. 

 Objects should remain in some 20 volumes of the fluid from 24 

 to 48 hours, according to size. It is well to change the fluid 

 once, after a few hours. After fixation, tissues should be washed 

 thoroughly in running water (6 to 12 hours) and passed through 

 alcohols of increasing strength beginning with 15 per cent. 



6. Bichromate of Potassium and Corrosive Sublimate (Zenker's 



fluid). - 



Corrosive sublimate 5 grams 



Potassium bichromate 2 grams 



Sodium sulphate 1 gram 



Glacial acetic acid 5 c.c. 



Water 100 c.c. 



It is best to add the acetic acid immediately before using. 

 Zenker's is a valuable reagent for both histological and embryo- 

 logical material (embryos up to 25 mm.). Several hoars are 

 required for fixation: 2 to 4 hours for a 2 day chick; 8 to 10 hours 

 for objects or embryos of 6 to 8 mm. ; 24 hours for embryos of 12 

 to 14 mm., etc. For washing, running water is employed for 

 from 12 to 24 hours. The object is then transferred to gradually 

 increasing strengths of alcohol up to 70 per cent., leaving it 

 according to size from 1 to 3 hours in each alcohol. To remove 

 the excess of corrosive sublimate, see 13, caution 1. Almost any 

 stain follows this reagent well. Both nuclear and cytoplasmic 

 structures are properly fixed. 



7. Bichromate of Potassium and Cupric Sulphate (Erlicki's 

 fluid). See chap, i, reagent 8 and chap. -in, 3. 



8. Bichromate of Potassium and Sodium Sulphate (Muller's 



fluid). - 



Bichromate of potassium 20 to 25 grams 



Sodium sulphate . 10 grams 



Water 1,000 c.c. 



Muller's fluid is an old and widely used reagent. It is espe- 

 cially valuable for the nervous system. It acts very slowly. 



