91 



after Hermann's fluid, as stains, Heidenhain's iron hematoxylin, Delafield's 

 hematoxylin, safranin (as a red stain), or gentian violet (as a blue stain). 



§24. Flemming's fluid ( Chrome-aceto-osmic ) . Formula: 1% aq. sol. 

 chromic acid, [5 parts; 2% aq. sol. osmic acid, 4 parts; glacial acetic acid, i 

 part; or, 10 aq. sol. chromic acid, 3 parts ; [% osmic acid, 16 parts ; glacial 

 acetic acid 2 parts ; water, 19 parts. This is a fine fixer and in most cases gives as 

 good results as Hermann's, and is not as expensive. It browns tissue less, and 

 while it blackens fat, does not blacken the myelin of myelinic nerve fibers 

 as does Hermann's. It should be employed in general in the same cases and 

 in the same way as Hermann's fluid. 



Fix tissue 1-24 hours (or longer); wash well in running water 2-24 hours ; 

 place in 67% and 82% alcohols, 12-24 hours in each. Bleaching of the sections 

 may be necessary, as with Hermann's fluid. Take only very small pieces of 

 tissue. Employ the same stains as with Hermann's fluid. 



§ 25. Picric alcohol. Formula : Distilled water, 250 c. c. ; 95% alcohol, 

 250 c. c. ; picric acid, i gram. A delicate fixer, penetrates well, and does not 

 make the tissue brittle or tough. It may be used with most tissues and organs. 



Allow it to act 1-3 days, changing to fresh each day if the bulk of tissue 

 is large, transfer to 67% alcohol for 1-2 days, 82% alcohol several days, chang- 

 ing -several times. If the paraffin method of imbedding is to be employed it 

 is best to leave the tissue in 82% alcohol until no more or very little color 

 comes away from it, as otherwise it affects the cutting quality of the tissue. 

 Most staining methods may be employed. Staining is good, though not quite 

 as brilliant as with mercuric chlorid fixers. 



J 26. Mercuric chlorid. One may employ (a) a saturated solution in 

 water, or better, {b) a. saturated solution in normal salt solution with 1-5% gla- 

 cial acetic acid. Water will dissolve about $%, normal salt solution about 12% 

 of the mercuric chlorid. This is a good fixer, especially when the piece is 

 small. It fixes as soon as it penetrates and is apt to make tissue brittle if it is 

 left too long. Staining after it is brilliant. The larger, percentage of acetic 

 acid is, perhaps, to be preferred for most histological objects. 



Fix the fresh tissue >^-24 hours according to the size of the piece. Re- 

 move to 67% alcohol for 1-2 days, 82% alcohol several days, changing often. 

 The 82% alcohol should contain enough tincture of iodin to give it a yellow 

 color, and fresh tincture added or (better) the alcohol changed when the yel- 

 low color of the iodin in the alcohol is lost. As long as the alcohol is decol- 

 orized, washing should be continued, since it is important that the mercuric 

 chlorid be all removed from the tissue ; otherwise precipitates will form in the 

 preparation after it is mounted or before, and spoil the result. Wash out in 

 alcohol thoroughly and carefully. Almost any stain may be employed after a 

 mercuric chlorid fixation. 



§27. Picro-aceto-sublimate. (vom Rath's fluid). Formula : SaXuraXeA 

 aqueous solution of picric acid, 50 c.c. ; saturated aqueous solution of mercuric 

 chlorid, 50 c.c. ; glacial acetic acid, i c.c. (1-5 c.c. according to the organ). 

 This is quite a satisfactory fixer if care is taken in its employment, combining 



