ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 901 



of specimens with various metal salts, such as chloride of palladium, 

 oxide of iron, &c. (2) Staining methods in which carmine is com- 

 bined with other reagents, e, g. picric acid, indigo-carmine, and metal 

 salts. (3) Methods in which logwood is used in combination with 

 various other reagents. (4) The combination of anilin dyes with 

 each other and with metal salts. (5) The combination of the gold 

 and silver methods. Not the least important and interesting part of 

 the articles is the historical description of the development of the 

 employment of anilin dyes in staining technique, commencing with 

 mauvein and fuchsin in 1856. The author well observes that those 

 who are engaged in histological research with the aid of staining 

 materials should be thoroughly acquainted with the chemistry of the 

 dyes with which they work, and a description is given of the source, 

 manufacture and properties of the anilin dyes as well as alizarin, 

 logwood, indigo, carmine, and others. 



In his concluding article,* Dr. H. Gierke has drawn up elaborate 

 tables respecting the anilin pigments. The first table gives the 

 ordinary nomenclature, chemical formulfe, remarks on the solubility, 

 reactions, and preparation of the various anilin stains. The second 

 table, arranged according to colour, gives the solubility in water or 

 alcohol and the behaviour with acid and alkalis. 



The rest of the paper is chiefly occupied with a discussion as to 

 whether, when a prei)aration becomes coloured, the colour is due to 

 imbibition of pigment, or is the result of chemical changes effected in 

 the tissue by the pigment. The author maintains that though histo- 

 logical staining depends for the most part on the physical processes 

 of diffusion and imbibition, the occurrence of chemical combination in 

 staining cannot be denied. On the contrary, such combinations are 

 of frequent occurrence and, as micro-chemical reactions, are of the 

 greatest importance. The histological stain, so far as it imparts a 

 permanent dye, depends on the physical process of surface attraction. 

 Chemical processes should be suspected when a pigment is discharged 

 or changes to a different shade. We may, therefore, speak of chemical 

 processes when one and the same pigment stains different tissue 

 elements of a preparation in different ways. Double staining by the 

 simultaneous or consecutive use of several dyes only in part depends 

 on chemical processes. In greater measure they arc effected by the 

 imequally developed attraction-force of various tissues. It is also 

 6ho^vn by the fact that one pigment is able to remove another from 

 certain tissue elements, but not altogether from the same preparation. 

 If a section of any organ, rich in various tissues, be laid in a mixture of 

 several pigments, each histtdogical element is stained by that for 

 which it possesses the greatest attraction. If a certain part have for 

 two or more dyes an exactly similar attraction, it then takes up both 

 or all, and a mixed colour is the result. Examples of staining by 

 chemical processes are, among others, the various reactions on amyloid 

 Bubstaiicc. When Curshmann employed methyl-green for staining 

 amyh^d degonorated nerves, all the normal parts were coloured 

 green, the hyaline cylinder light blue, and the amyloid substances 



• ZoitBclir. f. Wiss. Mikr., ii. (1885) pp. 1G4-221. 

 8er. 2.— Vol. V. 3 N 



