CHAPTER IV. 37 



only for very small objects or for very small pieces of tissue, such as 

 suffice for cytological or histological work. The strong liquid 

 especially has not the character^of a general reagent. As a matter 

 of fact it was recommended by FLEMMING in the first instance 

 merely for a very special purpose, the hunting for karyokinetic 

 figures, and not for general purposes. It is still very much used, 

 but in my opinion unadvisedly. In most cases, Bouin's picroformol 

 v, ill do all that it is intended to do, without its disadvantages. 



It may be used for prolonged hardening, e.g. of small pieces of 

 nervous tissue, and is very good for that purpose. 



Fat is blackened (or browned) by it. See 35. Chromatin is 

 mordanted by it for basic anilin dyes, enabling them to give peculiarly 

 sharp and powerful stains. 



42. Osmic Acid and Bichromate. ALTMAXN (Die Elementar- 

 organismen, Leipzig, 1890) takes for his " bioblasts " a mixture of 

 M j ual parts of 5 per cent, solution of bichromate of potash and 2 per 

 cent, solution of osmic acid. The bichromate ought not to contain 

 anv free chromic acid. Refer to 680. 



Lo BIANCO (Mitth. Zool Stat. Neapel, ix, 1890, p. 443) employs for 

 marine animals a mixture of 100 c.c. of 5 per cent, solution of bichromate 

 and 2 c.c. of 1 per cent, osmic acid. 



HOEHL (Arch. Anat. Phys., Anat. Abth., 1896, p. 31) recommends 

 a mixture of 80 c.c. of 3 per cent, bichromate, 20 c.c. of 1 per cent. 

 o.Mnic acid, and 2 c.c. of glacial acetic acid. 



43. Bichromate-chromic-osmic Acid. CHAMPY (Arch, de Zool. 

 Exper.. 1913). Mixture of 7 parts of 3 per cent, bichromate of 

 potash, 7 parts of 1 per cent, chromic acid, 4 parts of 2 per cent, 

 osmium tetroxide. 



This mixture keeps well. Fix for from six to twenty -four hours. 

 Wash out in running water about the same time. 

 You can stain in iron hsematoxylin. or less well in ALTMANN or 



V ' 



BEND A. See 681 for a description of mordanting after Champy's 

 fluid. This fluid is extremely useful, and I nearly always use it in 

 addition to FLEMMING. 



44. Osmic, Bichromate, and Platinic Mixture (LINDSAY JOHNSON'S 

 Mixture). Latest formula, 1895, communicated by Dr. Lindsay 

 Johnson : 



Bichromate of potash (2-5 per cent.) . .70 parts. 



Osmic acid (2 per cent.) . . . 10 ,, 



Platinum chloride (1 per cent.) . . . 15 ,, 



Acetic or formic acid . 5 ,, 



