130 HJIMATEIN AND OTHER ORGANIC STAINS. 



p. 177). Minot's account of these is as follows : " They may be employed 

 with sections of tissues hardened in various ways, and need not be confined 

 to Muller's fluid or chromic acid specimens (as in Weigert's process). The 

 sections are soaked first in a salt solution for ten to fifteen minutes. The 

 following aqueous salt solutions seem to be the most valuable : Alum, 2 per 

 cent. ; chromic acid, 1 per cent. ; bichromate of potassium, 5 per cent. ; ace- 

 tate of copper, nearly saturated. After soaking in one of these, the section 

 is passed quickly through distilled water, and placed at once in Weigert's 

 hsematoxylin (1 part of the crystals in 10 parts alcohol plus 90 parts water), 

 and may be left a short time for direct coloration, then washed and 

 mounted, or a longer time until they become black, and are to be washed out 

 by Weigert's iron solution (water 100, borax 2, ferricyanide of potassium 2^). 

 "The sections ought to be moved about constantly in the iron solution, other- 

 wise the colour will be extracted irregularly. The copper hsematoxylin goes 

 out very rapidly, so that with that stain it is better to dilute the iron solu- 

 tion with twice its bulk of water before placing the sections in it. After 

 the iron solution the sections must be washed very thoroughly in water, to 

 avoid further fading out, from which one is not entirely secure until the sec- 

 tions are actually mounted in balsam. 



"These methods are all merely modifications of Weigert's, Heidenhain's, 

 and Bohmer's methods." 



D. Other Organic Stains. 



200. Alizarin, so far as I am aware, is only used for Nerve-Centres. 

 See Part II. 



201. Purpurin is useful for cartilage and muscle. It is solu- 

 ble in a boiling aqueous solution of alum, from which it normally 

 precipitates on cooling, but may be prevented from doing so by 

 the addition of a certain proportion of alcohol. The employ- 

 ment of an alum solution as a vehicle for the colouring matter 

 has the advantage, at least so far as cartilage is concerned, 

 of fixing the cellular elements at the same time that they are 

 stained. (Ranvier found that alum in a solution of 5 1000 

 was the best of all fixing agents for cartilage-cells Traite, 

 p. 279.) 



KANVIER'S formula (Traite technique, p. 280). 200 grms. 

 of water and 1 of alum are boiled in a porcelain capsule ; 

 purpurin rubbed up in water is added, and the boiling con- 

 tinued. The purpurin being dissolved to saturation (this is 

 ensured by taking care to have an undissolved excess in the 

 capsule), the solution is filtered hot into a flask containing 

 60 c.c. of alcohol (36 Cartier = 90 per cent.). 



There is thus obtained a solution of an orange-rose colour, 

 presenting a marked degree of fluorescence. 



