12 



chlorid fixation. Its penetration is surprisingly good. The sodium sulphate is 

 probably unnecessary. Use of physiological (0.6%) salt solution instead of water 

 to prevent the formation of precipitates or the addition of a small amount of salt 

 to the fluid when made up for use, is recommended by some. 



Fix in Zenker's fluid 12 to 48 hours, wash well in water, running or frequently 

 changed, 12 to 48 hours, to remove the dichromate; transfer to 67% alcohol 

 for 1 or 2 days, 82% alcohol for several days, keeping in the dark while in the 

 alcohol. To the 82% alcohol add a drop or so of tincture of iodin, adding fresh 

 iodin or changing the alcohol when the color is lost. This should be continued as 

 long as the iodinized alcohol is decolorized in order to avoid a precipitate of the 

 mercuric chlorid in the tissue. Avoid, however, adding an excess of iodin, since 

 it will affect the staining quality of the tissue. Stain as you wish. 



13. Kelly's fluid. (Zenker-formol). Formula: Zenker's fluid, with 

 formalin substituted for the acetic acid. Potassium dichromate, 2.5 grams; 

 sodium sulphate, 1 gram; mercuric chlorid, 5 grams; formalin, 5 or 10 c. c., to be 

 added before using. Valuable for the fixation of cytoplasm and cytoplasmic 

 granules, where the acetic acid is to be avoided. Make up from the Zenker's 

 stock by adding the formalin. 



Fix 6 to 24 hours or longer, wash in running water 6 to 12 hours, alcohols. 

 If it is desired to give a longer mordantage in dichromate, transfer to Muller's 

 fluid or other simple dichromate solution. 



14. Dichromate-acetic. (Tellyesnicky's fluid) Potassium dichromate, 

 3 grms. ; glacial acetic, 5 c. c.; water, 100 c. c. This fluid gives good preservation 

 of nuclei and of the cytoplasm, the acetic acid checking the bad effects of the 

 dichromate. A simpler fixer than Zenker's fluid. 



Fix 1 to 14 days according to the size of piece and the object. Wash in 

 running water 12 or 24 hours, and pass up through 25, 50, 67, and 82% alcohols, 

 12 to 24 hours in each. 



15. Formol-Dichromate (Orth's fluid). Formula: Potassium dichro- 

 mate, 2.5 grms. ; sodium sulphate, 1 grm.; water, 100 c. c. (i. e., Muller's fluid); 

 formalin, 10 c. c. A good fixer of cytoplasm, but an indifferent one for nuclear 

 detail. It has been especially used in the case of the nervous system ( 199). 

 Other proportions of formalin and dichromate may be taken, the sodium sulphate 

 being omitted. It should be freshly made up as it soon deteriorates. 



Fix 3 to 24 hours or longer, wash in running water 12 to 24 hours; 50, 67, 

 82% alcohols, 1 day in each. If a long fixation is given, the fluid should be 

 frequently changed. 



16. Copper dichromate-sublimate-acetic. Formula: 10% copper dichro- 

 mate, 1 part; 4% copper sulphate, 1 part; sat. solution mercuric chlorid, 2 

 parts; glacial acetic acid, rV to 5%, according to need. Similar to Zenker's 

 fluid in its general properties and should be used in the same way. Excellent as a 

 preserver of cytoplasmic granules of lipoid nature ( 177-9). A further mordan- 

 tage in 2.5% copper dichromate is often advantageous (3 to 4 days). 



By the substitution of formalin (5 to 10%) for the acetic acid, a fixer compar- 

 able to Kelly's fluid ( 13) is obtained. 



17. Picro-aceto-formol. (Picro-formol). Formula: Picric acid, satu- 

 rated aqueous solution, 75 c. c.; formalin, 25 c. c.; glacial acetic acid, 4 c. c. 



