16 - Fixation (chap. 1) 



Good substitute for Zenker's if dichromate is not required. Hardens 

 less. Rapid penetration. Go directly to 70% alcohol. Post-treat for 

 mercuric chloride. 



Zenker's fixative: 4-24 hours. If tissue seems to harden excessively, 

 follow a maximum of 18 hours in Zenker's with a 12-24 hour chro- 

 mating in 3% potassium dichromate. 



potassium dichromate 2.5 gm. 



mercuric chloride 4.0-5.0 gm. 



sodium sulfate 1.0 gm. 



(may be omitted, see indifferent salts, page 10) 



distilled water 100.0 ml. 



glacial acetic acid 5.0 ml. 



Excellent general fixative, fairly rapid penetration. Wash in running 

 water overnight. Post-treat for mercuric chloride. Zenker's may serve 

 for Helly's (page 14) if acetic acid is not added to the stock solution. 



Fixatives for Cell Inclusions and Special Technics 



altmann's fixative {Gatenby, 1930): 12 hours. 



5% potassium dichromate 10.0 ml. 



2% osmic acid 10.0 ml. 



Good for fat and mitochondria. 

 Wash in running water overnight. 



ammerman's fixative {1950): 2 hours. 



chromium potassium sulfate (chrome alum) ... 3.0 gm. 



formalin 30.0 ml. 



glacial acetic acid 2.0 ml. 



distilled water 238.0 ml. 



Good for yolk-rich material and insect larvae. Do not fix longer than 

 2 hours, or swelling occurs. Does not harden and gives good cytologi- 

 cal detail. Wash in 70% alcohol or water. 



CARNOY fixative (Gatoiby, 1930): 3-6 hours. 



Formula A: 



glacial acetic acid 20.0 ml. 



absolute ethyl alcohol 60.0 ml. 



