1896.1 MICROSCOPICAL JOURNAL. 353 



covering epitheliain or have overrun the collagen tissue 

 of the muscles of the skin. In such cases the nuclei 

 naturally appear just so much clearer the more the re- 

 maining tissue is decolorized. 



Such a demonstration of mast-cell nuclei can be very 

 easily combined with the methylene blue staining method. 

 Either color slowly in a weakened solution, or decolorize 

 the over-stained sections in glycerine, ether solution or 

 mineral acid. As a bleaching addition to the polychrome 

 methylene blue solution alum has shown itself valuable. 

 We put as much alum as can be held on the point of a 

 knife in a saucer of staining solution and leave the 

 sections therein for an hour or even over night. They 

 are then, after a washing with water, put directly in abso- 

 lute alcohol, oil and balsam. The nuclei themselves are 

 very plain ; the mast-cell nuclei are dark, cherry red, and 

 the remaining tissue is pale blue. For demonstrating 

 the isolated mast-cell nuclei in tissue there is no surer 

 method than that by means of decolorizing with the 

 above mentioned mixture of glycerine and ether. We 

 allow the sections to remain in the undiluted mixture 

 until they are of a clear blue color ; then wash them in 

 water and put them in alcohol, oil and balsam. One is 

 always sure by this method of decolorizing to extract all 

 the blue from the nuclei without damaging the red color. 

 In the second place, we can take into consideration 

 the mineral acids, and we have found the best to be 

 nitric and hydrochloric. The section is first put in a five- 

 per-cent nitrate of potash solution for from twenty to 

 thirty seconds in a saucer, and then from ten to twenty 

 seconds in a saucer with a few drops of acid alcohol ; 

 then in absolute alcohol, etc. Simple acid decolor- 

 ization generally leaves still a faint trace of blue in the 

 nuclei. 



But at the same time that isolation of the mast-cell 



