80 THE AMERICAN MONTHLY [April, 



stained. The color is entirely and quickly removed by alkaline alcohol. 

 The author uses this dye in combination with haeraatoxylin in the place 

 ofeosin. It has the advantage over the latter that it is not withdrawn 

 from the sections by alcohol or any of the clearing media, while it is 

 withdrawn from the celloidin. He uses it in dilute aqueous solutions 

 and does not stain the sections too deeply, and then withdraws the color 

 from the celloidin with alcohol. 



Benzopurpurin 4b. — An orange red dye, freely soluble in alcohol. 

 It stains diffusely. Sections are placed in the staining solution from 

 alcohol and stain for a few moments only. Connective tissue stains 

 orange, the nuclei of a slightly darker shade ; the celloidin stains lilac. 

 The stain is altered slightly by acids and alkalies. Alcohol extracts a 

 part of the color, especially from the celloidin. This dye is best used 

 in combination with hiematoxylin, but the sections must be washed in 

 water before placing in the haematoxylin because of the acidity of the 

 benzopurpurin. 



Deltapurpurin. — A brownish-red powder, freely soluble in water. 

 The aqueous solution stains sections, in two minutes, a diffuse purple- 

 red color. The color is not withdrawn from the tissues by alcohol, 

 acids, or potassa. Alcohol withdraws the color from the celloidin after 

 an half hour. Acids change the color in the celloidin to a bluish tint. 

 This dye is to be used in combination with hcematoxylin, the latter be- 

 ing used first and then a faint stain with the deltapurpurin. Then wash 

 well in water and withdraw the color from the celloidin with alcohol. 

 Connective tissue stains red, somewhat on a violettint ; nuclei stain bluish. 



Benzo-Azurin. — A brownish powder that dissolves easily in water 

 with a blue-violet color. Concentrated solutions stain quickly, weak 

 solutions slowly. A weak solution is to be preferred. All tissue ele- 

 ments as well as the celloidin stain ; nuclei of a darker shade than the 

 protoplasm. Sometimes the connective tissue elements stain of a reddish 

 tint, the nuclei of a htematoxylin color. This may be due to the reac- 

 tion of the tissues. Alkalies change the color of the solution to red ; 

 they also completelv decolorize stained sections. Alcohol withdraws 

 the color slightlv from the tissues and the celloidin. Clearing and 

 mounting media do alter the color. Acids do not change the color, 

 consequently decolorization must be done in alkaline solutions. 



This dye stains quickly and intensely, resembling hematoxylin some- 

 what in the results, although the nuclei do not stain as sharply as with 

 the former. Beautiful pictures are obtained in the skin and kidney. 

 In sections of the central nervous system, the neurolgia and the branches 

 of Purkinje's cells are especially sharp. 



Chrysophenin. — A sulphur-yellow dye, slightly soluble in water, 

 easily so in alcohol, in which sections are to be stained. The staining 

 is quick and diffuse, the color bright yellow. Alcohol extracts the color 

 from the celloidin, but the color in "the tissues is not affected by either 

 alkalies or acids. 



Rhodanin-red and Rhodanin-violet. — Two basic dyes soluble 

 in both alcohol and water with a strength of color equal to that of fuch- 

 sin. Solutions of these dyes stain, diffusely, a carmin-red and reddish- 

 violet. Water and alcohol extract the color from the sections, so they are 

 of no use for histological work. Bacteria stain, but as yet no method of 

 fixing the dye has been found. Further experiments are being carried on. 



