OYTOLOGICAL METHODS. 363 



The defect of want of penetration seems to be incurable 

 (see 28, 39, and 46). Substitution of more highly pene- 

 trating reagents, such as picric acid, for the chromic acid 

 or platinic chloride, does not help in the least ; you only get 

 the osmic fixation outside, no whit deeper than before, and a 

 picro- acetic fixation, instead of a chromo- or platino-acetic 

 one, in the deeper layers, fhat is all. For instance, vom 

 Rath's picro -platinosmic mixture, 97, may often give better 

 results in some respects than liquid of Hermann ; but that is 

 not on account of the addition of the picric acid, it is rather 

 on account of the platinic chloride being taken weaker. 

 The osmic fixation is not in the least modified by the picric 

 acid in it. 



In view, then, of these defects of osmic mixtures, it may 

 often be advisable, where hyaloplasm, or its inclosures, is the 

 chief object of study, to have recourse to bichromate of potash. 

 The formula that has given me the finest fixations is that of 

 LINDSAY JOHNSON, 49, but it has the drawback that there is 

 risk of osmication in the outer layers. 



In this respect liquid of Telly esniczky, 56, is to be pre- 

 ferred. 



Corrosive sublimate gives a fairly full fixation ; but I 

 believe it sometimes produces serious artefacts, HEIDENHAIN'S 

 " Lanthanin " being one of them. I have, however, obtained 

 with liquid of Gilson-Carnoy-Lebrun some most excellent 

 fixations of cytoplasm, and I think that the aqueous solutions 

 of sublimate may frequently be used in preference to liquid 

 of Flemming on account of the facilities they afford for the 

 employment of certain stains. 



ALTMAXN'S fixatives for nuclei see last edition, or Arch. Anat. Entw., 

 1892, p. 223, and his Elementarorganismen, 1890. His mixture for his 

 granula see 48. 



649. Chromatin Stains. For fresh tissues see 646. 



For sections of hardened tissues, stains should be chosen 

 amongst, those that give a very intense as well as a very 

 sharp coloration. Some years ago safranin and gentian 

 violet, 272, 273, were the most used. At the present 

 time their place has been taken by the iron haematoxylin of 

 BENDA or HEIDENHAIN. 



To these I think Kernschwarz should be added. 



