XIV, 2. Eisen: Notes on fixation, stains, the alcohol method, etc. 199 



staining. For scientific investigations of cell structure and cell 

 Differentiation, both hsematoxylin and brazilin have bat little use; bat 

 for elasswork or for pathological examinations brazilin is a desirable 

 stain. For botanical sections brazilin is a very good stain, sure 

 and rapid, staining nnclei with strength and precision. It has an 

 advantage over hsematoxylin in that it may be washed out to some 

 extent without losing in brilliancy. Botanical sections stained with 

 brazilin may be differentiated in alcohol of 95 per cent. for several days, 

 improving steadily. Even with the highest Systems of lenses the 

 nnclear chromatin and linin threads show no diffuse staining, but 

 stand out boldly and clearly. 



Brazilin should be mixed the same asBöHMEit's hsematoxylin. After 

 a few weeks the stain ripens into a deep , brilliant red , with good 

 staining qualities ; but at the same time numerous blue tlakes are 

 precipitated in the stain, which soon turns so cloudy as to become 

 opaque. These tlakes, which appear blue under the microscope, do 

 not dissolve in water. Chemically they probably stand to brazilin 

 as hsematein to hsematoxylin. They possess, however, extraordinary 

 staining qualities. I use them as follows : Filter the original bra- 

 zilin stain through as small tilter-papers as possible ; scrape off the 

 bluish deposit, together with some of the paper, and dissolve this in 

 alcohol of 95 per cent., adding 15 per cent. or more of glycerine. This 

 Solution is intensely red, does not precipitate, and stains nuclei deep 

 red. It is a much better stain than the original Solution. The orig- 

 inal filtered Solution will again precipitate and the tlakes may be 

 used and dissolved as at first. As a counter stain, nse nigrosine or 

 indulin in weak Solutions. The stain is permanent and does not 

 deteriorate. Nearly all aniline stains give better results if mixed 

 with 10 to 15 per cent. glycerine. 



Iron-hcematoxylin. Weak Solutions are preferable to strong 

 ones. The liquor ferri sulfurici oxydati, I use diluted at least live 

 times. Immersion should be for about 12 hours or more. The slides 

 with the sections should be washed for at least one minute in 

 water before being placed in the hsematoxylin bath. I prefer to 

 have the lmematoxylin weak. The saturated Solution (watery) should 

 be made up in quantity, and should contain 10 per cent. or more 

 alcohol, in order not to degenerate. It improves greatly with age, 

 becoming darker when ripe. YVhen used, it may be diluted with from 

 ten to twenty times the amount of distilled water. If tap water is used 



