186 chaptkt; xv. 



Kern imd Protoplasma, p. 1]6); for this see fourtli edition. See also 

 Israel {PraUilcum Path. Hist.,^ AuS., Berlin. 1893, p. 69); Teambtjsti 

 {Ricerche Lab. Anat. Roma, v. 1896, p. 82 ; Zeit. wiss. Mik., xiii, 1896, p. 

 357) : and Thome (op. cit. supra). Bisen (Proc. Calif. Acad. [3], i, 

 1897, p. 8) acidifies witli oxalic acid. 



After acidification tlie solution must not be filtered, and if 

 it has been kept for some time a little more acid must be 

 added. 



Before staining (M. Heidenhain, lac. cit.), sections should 

 be treated for a couple of hours with O'l per cent, acetic 

 acid, then for ten to fifteen minutes with officinal tincture of 

 iodine, and be rinsed with alcohol before bringing into the 

 stain. The treatment with acid is necessary in order to 

 ensure having the sections arid on mounting in balsam. The 

 primary object of the iodine i.s to remove any sublimate 

 from the preparations, but it also is said to enhance the power 

 of staining of the chromatin with methyl green, and to 

 produce a more selective staining of protoplasmic elements. 

 The stain is a very fine one when successful. But it is 

 very cafiricious. The correct result should be a precise 

 chromatin stain combined with a precise stain of the plastin 

 element of cytoplasm by the Saurefuchsin. Now the least 

 defect or excess of acidity causes the plasma stain of the 

 Saurefuchsin to become a diffuse one, instead of being 

 sharply limited to the plastin element. It is difficult to 

 dehydrate the sections without losing the methyl green. 

 For this reason the stain will only work with very thin 

 sections: to be quite sure of good results, the sections should 

 be of not more than 3 /i in thickness, and if they are over 

 5 the desired results are almost hopeless. The stain 

 keeps very bad]}-. I admit that the method has its raison 

 d'etre for the very special objects for which it was imagined 

 — for the researches on cell-granulations for which Ehelich 

 employed the three colours, or for the researches on the 

 plastin element of cytoplasm for which Maetin Heidenhain 

 employed the mixture ; for the study of gland cells ; and 

 for similar objects. But to recommend it, as has been done, 

 as a general stain for ordinary work, is nothing but mis- 

 chievous exaggeration. For it is far from having the 

 qualities that should be possessed by a, normal section stain. 



