38 CHAPTEE IV. 



HoEHL {Arch. Anat. Phys., Anat. Ahth., 1896, p. 31), 

 vecommends a mixtm-e of 80 c.o. of 3 per cent, bichromate, 

 20 CO. of 1 per cent, osmic acid, and 2 c.o. of glacial acetic 

 acid. 



44. Osmic, Bichromate, and Platinic Mixture (Lindsay John- 

 son'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 ,, 



Hbnnegdt, who has worked a great deal with this reagent, 

 and recommends it highly, says (Leqcms sur la Cellule, p. 61) 

 that it is well only to add the acetic or formic acid just before 

 using, as it frequently reduces the osmium and platinum 

 very rapidly and energetically. He finds that it contracts 

 the more spongy sorts of protoplasm less than mixture of 

 Flbmming. I think highly of it— for certain objects. 



45. Platino-aceto-csmic Acid (Hermann's solution {Arch. mik. 

 Anat., xxxiv, 1889, p. 58). One per cent, platinum chloride 

 15 parts, glacial acetic acid one part, and 2 per cent, osmic 

 acid either 4 parts or only 2 parts. Hermann found that 

 protoplasmic structures are thus better preserved than witb 

 the chromic mixture. 



The after-treatment and staining should be the same 

 as for objects treated with Flemming's solution. Rengel 

 (Zeit. wiss. Ziol., Ixiii, 1898, p. 454) washes out for half an 

 hour to an hour with saturated aqueous sol. of picric acid, 

 which he thinks facilitates the staining, especially of nuclei. 



The action of this fixative is, roughly, similar to that of 

 Flemming's. Like Flemming's, it mordants chromatin for 

 staining with " basic " colours, with which it affords equally 

 fine nuclear stains. But, owing to the platinum in it, it 

 diminishes more than Flemming's the colorability of tissues 

 with " acid " colours, so that it is extremely difficult to 

 obtain good plasma stains after its action. It causes a 

 notable shrinkage in chromatin. It gives a full fixation of 

 cytoplasm, to which it gives a much more fine-grained 

 aspect than liquid of Flemming does. 



