H^MATOXYLIN. 93 



169. Alum Cochineal (PARTSCH, Arch.f. mik. Anat., xiv, 1877,. 

 p. 180). Powdered cochineal is boiled for some time in a 5 

 per cent, solution of alum, the decoction filtered, and a little 

 salicylic acid added to preserve it from mould. 



170. Alum Cochineal (CzoKOR, Arch.f. mik. Anat., xviii, 1880, 

 p. 413). Seven gr. cochineal and 7 gr. calcined alum are 

 rubbed up together into powder in a mortar, add 700 gr. distilled 

 water, and boil down to 400 gr. When cool, add sufficient 

 carbolic acid to be perceptible by the smell, and filter several 

 times. The violet solution is ready for use, and will keep for 

 six months, after which time it must be filtered again, and a 

 fresh trace of carbolic acid added. 



This stain possesses considerable elective faculty, and is 

 stated to stain, in a longer or shorter time, all kinds of tissue, 

 no matter in what way they may have been hardened. Nuclei 

 are stained haematoxylin colour, and other elements different 

 tones of red, so that the effect is that of a double stain with 

 haematoxylin and carmine. Alcohol objects require three to 

 five minutes, chromic objects three to five hours. 



The formula known as Klein's cochineal fluid (which appears to have been 

 first published in the Ann. and Mag. Nat. Hist., viii, 1881, p. 232) is iden- 

 tical with that of Czokor. 



171. Borden (The Microscope, 1888, p. 83) has proposed an alcoholic 

 alum-cochineal, which consists of an alum-cochineal similar to that of 

 Partsch, combined with an equal volume of 95 per cent, alcohol. I doubt 

 the success of this modification. 



B. H^MATOXYLIN. 



172. The Use of Hsematoxylin. We have the coal-tar colours 

 for staining sections, and we have carmine and cochineal for 

 staining in the mass. What, then, do we want haematoxylin 

 for ? The answer is, that we sometimes want it for staining 

 in the mass on account of the faculty it has of readily staining 

 tissues that have been treated with chromic and osmic mixtures. 

 This it does in general better than any carmine or cochineal. 

 We want it also for some special purposes, such as staining the 

 NebenJcern and achromatic figure of nuclei ; and for nerve- 

 researches, and other special histological objects. 



173. General Remarks. None of the solutions of haematoxylin 

 are perfectly stable ; only one or two are fairly so. 



