CHAPTER XIX. 



OTHER STAINS AND COMBINATIONS. 



365. Kernschwarz (PLAINER, Zeit. f. u-iss. Mik., iv, 3, 

 1887, p. 350; Journ. Roy. Mic. Soc., 1888, p. 675). Kern- 

 schwarz is a black liquid prepared for liistological purposes 

 by a Russian chemist, and imported by Grubler & Hollborn. 

 Its exact composition is unknown, but it is certainly an ink. 

 MAYER (Grundzuge, p. 202) finds that it contains a metallic 

 base, namely iron, combined with an organic acid, which is 

 highly probably some gallic acid. The liquid keeps in- 

 definitely, and affords a progressive or regressive stain, 

 according to circumstances. I use it as follows : 



Sections (I have not tried material in bulk) are fixed on 

 slides and treated with Kernschwarz until they become grey 

 or black. If the material is fresh, the required depth of 

 stain may be obtained in a few minutes, and in that case it 

 may be well to first dilute the Kernschwarz with about ten 

 volumes of water if it be desired not to run the risk of over- 

 staining. If the material is not fresh, that is if it has been 

 kept for some months, it will be necessary to stain for 

 twenty-four hours in the undiluted liquid. 



There is obtained a black or neutral-tint stain, which is, 

 according to the previous treatment of the material, either a 

 pure chromatin stain, or at the same time a plasma stain. 

 If overstaming should have occurred, or if there has been 

 obtained a plasma stain that it is desired to remove, the 

 stain is easily differentiated by means of any weak acid, 

 either in water or alcohol. PLATNER took alkalies, preferably 

 carbonate of lithia, for differentiation ; but that is clearly 

 faulty practice. 



