644 TECHNIQUE 



Pieces of tissue are left in the fluid for one to six weeks ; large 

 pieces of the spinal cord or brain require four to six weeks. If left 

 too long the tissues will become brittle. After fixation, the tissue 

 is washed thoroughly in running water for twelve to twenty-four 

 hours, and hardened in graded alcohol. 



A relatively large volume of the fixing fluid should be used, 

 and it should be frequently changed. It should not be allowed to 

 become turbid nor to deposit crystals : this is avoided by frequent 

 changes and by keeping the jars in the dark, or at least in such a 

 position that they are not exposed to a bright light. 

 Tellyesniczky's Fluid : 



Potassium bichromate 3 grm. 



Glacial acetic acid 5 cc. 



Water 100 cc. 



Pieces of tissue are placed in a considerable volume of the fixing 

 fluid and left for three to seven days. They are then washed in run- 

 ning water for twelve to twenty-four hours, and hardened in 

 graded alcohol. This fluid yields excellent results with muscular 

 and glandular tissues, and is particularly serviceable where pieces 

 of considerable size must be used, e. g., whole embryos. 

 Miiller-Formol : 



Mailer's fluid 95 to 90 cc. 



Pure formalin 5 to 10 cc. 



This is an excellent fixative for general use, for by it most tis- 

 sues are well preserved. Small pieces of tissue are left in a con- 

 siderable volume of the fluid for one to five days, washed thoroughly 

 in running water for twelve to twenty-four hours, and hardened in 

 graded alcohol. The washing should be so thorough as to remove 

 all excess of the chromium compounds, otherwise difficulty will be 

 experienced in obtaining satisfactorily stained preparations. 

 Zenker's Solution : 



Potassium bichromate 2.5 grm. 



Sodium sulfate 1 grm. 



Mercuric chlorid . . 5 grm. 



Distilled water 100 cc. 



Just prior to use add 1 cc. of glacial acetic acid to each 20 cc. of 

 the fluid. 



Small pieces of tissue, only, should be used. They remain in a 

 considerable volume of the solution for three to twenty-four hours, 

 after which they are thoroughly washed in running water for 

 twelve to twenty-four hours, and hardened in graded alcohol. A 



