CYTOL'OCUCAL METHODS. 323 



one eighth of the prescribed amount without loss of the dis- 

 tinctive characters of the fixation. 



The defect of want of penetration seems to be incurable 

 (see 35 and 42). Substitution of more highly penetrat- 

 ing reagents, such as picric acid, for the chromic acid or 

 platinum 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 chrqmo- or platino-acetic 

 one, in the deeper layers, that is all. 



In view of these defects of osmic mixtures, it may 

 often be advisable, where hyaloplasm, or its enclosures, 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, but it has the drawback that there is 

 risk of osmication in the outer layers. 



In this respect liquid of Tellyesniczky, 52, is to be 

 preferred. 



Corrosive sublimate gives a fairly full fixation ; but I 

 believe it frequently produces serious artefacts, HEIDENHAIN'S 

 " Lanthanin ' being one of them. Hcidenhaiir's solution, 

 64, containing as it does some 11 per cent, of sublimate, 

 without the addition of any acid to neutralise its shrinking 

 action, seems to me to be an inadmissibly coarse reagent. 

 I have, however, obtained with liquid of Carnoy-Lebrun, 86, 

 some most excellent fixations of cytoplasm. The aqueous 

 solutions of sublimate are frequently used in preference to 

 liquid of Flemming on account of the facilities they afford 

 for the employment of certain stains ; but to that end I 

 prefer BOUIN'S picro-f ormol . 



ALTMANN'S fixtives for nuclei see fifth edition, or Arch. Aunt. 

 1802, p. 223, and his Elementarorgamsmen, 1890. His mixture for his 

 graiiula see 43. See also THEOHARI (Journ. de I'A-nat., xxxvi, 1900, 



p. 216). 



(2) The same with a saturated aqueous solution of corrosive 

 sublimate instead of the water. 



They are both of them, in my opinion, as ill-imagined as possible. 

 They contain some three times as much platinum chloride as Hermann's, 

 and Hermann's contains already quite as much as it can bear, and, I 

 think, much more than is advisable : see the proportions in the mixtures 

 44 and 49. RABL (An at. Anz., iv, 1889, p. 21) employed it of from 

 T \Y to i per cent, strength, which seems to me much nearer the mark. 



