122 HJIMATE'IN AND OTHER ORGANIC STAINS. 



with acid. A good staining solution should not be blue-violet ; if it be, it 

 should be corrected by cautious addition of acid. But it is better to avoid 

 having an excess of aluminium salt. 



Mayer then gives some hints concerning the ingredients of staining solu- 

 tions such as we are here considering. Aluminium chloride should not be 

 damp. It should have a strongly acid reaction. The alcohol and the vessels 

 used should not have an alkaline reaction. The test for this is that a weak 

 solution of haematem in the alcohol should not turn purple ; or that a solu- 

 tion of 1 part each of hseniatein and aluminium chloride in 100 parts of 

 alcohol being added to the alcohol, in the ratio of 1 : 100, should not precipi- 

 tate in the course of twenty-four hours. The calcium chloride should have 

 a neutral or feebly alkaline reaction, and should not be damp. 



In view of the above criticism, the correctness of which, in the main at 

 least, will be acknowledged by all who have worked with Kleinenberg's 

 solution, I think it is quite time that it should be discarded, and Mayer's 

 hsemacalcium used instead in all cases in which a powerful, alcoholic hsema- 

 te'in stain is indicated (e. g. for staining in bulk large impermeable objects 

 that have been fixed in osmic or chromic mixtures). 



If, however, it be used, the following points should be observed : The solu- 

 tion should be allowed to ripen before using (Kleinenberg's practice was the 

 contrary of this, and, I conceive, erroneous). Small objects are best stained 

 slowly with a very dilute solution. If it be required to dilute a solution 

 already prepared for staining, this should not be done with alcohol, which 

 may easily cause precipitates to form on the tissues, but with the above- 

 described solution of alum in calcium chloride solution. Over-stains should 

 be washed out with acidulated alcohol. Either oxalic or (^ per cent.) hydro- 

 chloric acid may be used, and the specimens allowed to remain in them until 

 they begin to acquire a reddish hue. The acid is then removed by pure 

 alcohol, which restores the pure blue of the stain. It must be very 

 thoroughly removed in order to ensure the permanence of the stain. 



For large or impermeable objects immersion for days in a very strong 

 solution may be necessary for staining. Osmium and chromic acid objects 

 stain sufficiently. 



185. Delafield's Hsematoxylin (Zeit. f. wiss. Mik., ii, 1885, p. 288). 

 The history of this formula is as follows : It had long been in use in the 

 Institute of Pathology at Heidelberg, when it was communicated by Pfitzner 

 to Flemming, who published it and particularly recommended it in his 

 Zellstz., &c., p. 388, 1882. Flemming then attributed the formula to 

 Grenadier, and in consequence the stain went for years by the name of 

 "Grenadier's hseinatoxylin." Later on Memrning discovered that this 

 attribution was erroneous, and attributed, the formula to Prudden ; and in 

 consequence it was thenceforth known for some time as " Prudden's ha3ma- 

 toxylin." In 1885 matters were set right by Prudden's explaining that the 

 stain was the invention of Delafield, and publishing the correct formula here 

 quoted (in the formula as published by Flemming the proportions are some- 

 what different). 



To 400 c.c. of saturated solution of ammonia- alum* add 

 * Ammonia-alum dissolves in about 11 parts of water. 



