156. CHAPTER XIII. 



stain,, not hwmatein, the iron salt oxidising it into liauna- 

 tein, or into a higher oxidation product. I have obtained 

 some good stains with hasmatein, but also some very bad 

 ones ; presumably the solutions easily over-oxidise on con- 

 tact with the iron salt. 



The hasmatoxylin is generally dissolved in water. I 

 frequently prefer alcohol, of 50 per cent., as less injurious 

 to tissues. 



The method is a regressive one. It has been proposed to 

 stain progressively, which I have tried, and had extremely 

 bad results. 



The differentiation requires to be carefully timed. For 

 this reason the method is only applicable to sections, which 

 should be thin, best not over 10 ft. 



Iron haematoxylin is one of the most important of stains. 

 It enables us to stain elements which cannot be selectively 

 stained in any other way. The stain is very powerful, and 

 of a certain optical quality that is peculiarly suited to the 

 employment of high powers ; it will allow of the use of 

 deeper eye-pieces than otlier stains. It will take effect on 

 any material, and is quite permanent. Further details as 

 to the characters of the stain are given in 242. 



241. BENDA'S later Iron Hsematoxylin (Verb. d. Anat. GW., 

 vii, 1, 1893, p. 161). Sections are mordanted for twenty- 

 four hours in liquor ferri suphurici oxidati, P.G-., 1 * diluted 

 with one or two volumes of water. They are then well 

 washed, first with distilled water, then with tap water, and 

 are brought into a 1 per cent, solution of hsematoxylin in 

 water, in which they remain till they have become thoroughly 

 black. They are then washed and differentiated. The 

 differentiation may be done either in 30 per cent, acetic 

 acid, in which case the progress of the decoloration must 

 be watched ; or in a weaker acid, which will not require 

 watching ; or in the sulphate solution strongly diluted with 

 water. 



I find that if the iron solution be taken for the differen- 



* This preparation consists of sulphate of iron, 80 parts ; water, 40 ; 

 sulphuric, acid, 15 ; and nitric acid,. 18, and contains 10 per cent, of Fe. 

 Doubtless the ferri per&ulplia,ti& /.'</or B. P. will do instead ; the point 

 is, to have a per-salt, and not a proto-salt. 



