188 CHAPTER XIII. 



The method may be varied by washing out after staining with alum solu- 

 tion (1 per cent.) instead of a chromate. In this case the stain will be blue. 



253. APATHY'S Modification of Heidenhain's Process (Zeit.f. wiss. 

 Mik., v, 1, 1888, p. 47). This is an alcoholic method. , Stain in a 1 percent, 

 solution of hcematoxylin in 70 or 80 per cent, alcohol. Wash out (for 

 " thin " sections, i. e. sections of 10 to 15 /i, half the time of staining for 

 " thicker" sections of 25 to 40 /* twice the time of staining) in 1 per cent, 

 solution of bichromate of potash in 70 to 80 per cent, alcohol. 



The bichromate solution is conveniently prepared by mixing one part of a 

 5 per cent, aqueous solution with about four parts of 80 to 90 per cent, 

 alcohol. The mixture should be made immediately before using, and should 

 be kept from the light (light precipitates it) during the process of decolora- 

 tion, and should also be changed for fresh several times during the process. 

 After the differentiation of the colour has been accomplished, the objects 

 should be thoroughly washed (still in the dark) in several changes of 70 per 

 cent, alcohol. 



Preparations made in this manner are said to be more transparent and 

 better preserved than those made by Heidenhain's process. 



For celloidin series of sections, Apathy (Zeit. /. wiss. Mik., vi, 2, 1889, 

 p. 170) stains in the haematoxylin solution as above for ten minutes ; then 

 removes the excess of hsematoxylin fluid from the sections by means of 

 blotting-paper, and brings the series for five to ten minutes into 70 per cent, 

 .alcohol containing only a few drops of a strong (5 per cent. ^solution of 

 bichromate. This must be done in the dark. If the hjEinatoxylin be not 

 removed with blotting-paper as described, the celloidin will take the stain. 

 The sections should appear steel-blue to steel-grey. 



254. BENDA'S later Iron Haematoxylin (Verh. <L Aimt. Ges., 

 vii, 1, 1893, p. 161 ; Zeit. f. wits. Mik., xi, 1, 18^4, p. 69; 

 for his earlier method see Arch. Anat. PJiys., Pliys. Abth., 

 1886, p. 564). Tissues fixed in any way may be employed. 

 Sections are mordanted for twenty-four hours in Liquor ferri 

 sulphurici oxidati, P. Gr._, diluted with one or two volumes of 

 water (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). They are then well washed, first with 

 .distilled water, then with tap-water, and are brought into a 

 i per cent, solution of haematoxylin 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 pro- 

 gress 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. 



