STAINING AGENTS AND METHODS. 25 



STAINING AGENTS AND METHODS. 



STAINING FLUIDS. 



It is a very interesting fact (and one upon which our present 

 knowledge of histology largely depends) that, on examination of tis- 

 sues which have been dyed with special colored fluids, the dye will 

 be found to have colored certain anatomical elements very deeply, 

 others slightly, while others still remain unstained. Not only are 

 different depths of color thus obtained, but different tints, even with 

 a single dye, are often presented. If a section of some animal tissue 

 be immersed in a mordanted solution of logwood, for example, besides 

 the different depths of blue which are communicated to certain 

 parts, other elements present pink and violet tints in various shades. 



The rule concerning the selection of dyes seems to be that those 

 elements of a tissue which are the most highly endowed physio- 

 ogically take the staining most readily. The minute granules of 

 nuclei are so deeply stained in the logwood dye as to appear almost 

 black. The nuclei are plainly stained, while the limiting membrane 

 of cells is usually but slightly colored. Old, dense connective tis- 

 sues stain feebly, or fail entirely to take color. The differentiation 

 is, without doubt, due to chemical action between the elements of 

 the dye and those of the tissue. 



A very great number and variety of materials have been used for 

 histological differentiation, and a simple enumeration of them all 

 would very nearly fill the remainder of our pages. It will be found, 

 however, that leading histologists confine themselves to two or three 

 standard formulae for general work. I shall notice only those 

 methods which have been thoroughly demonstrated by years of em- 

 ployment as best for the purpose suggested. Special cases will re- 

 quire special treatment, which will be indicated in proper connection. 



H^MATOXYLIN * STAINING FLUID. 



To about eight fluid-ounces of a hot, saturated aqueous solution 

 of common alum, contained in a porcelain capsule, add, a few grains 

 at a time, one drachm of hcematoxylin, with constant stirring. Boil 

 over the spirit lamp very slowly for fifteen minutes. Add sufficient 

 water to compensate for evaporation; and, when cold, pour into a 

 wide-mouth bottle. Throw in a piece of camphor, say 30 grains, 



* The coloring principle of the Hsematoxylon Campechianum. Merck's pre- 

 paration should be used. 



