90 METHYLEN BLTJti, AND OTHER ANILINS. 



nuclear stain, according to MAKTIN (see Journ. Roy. Mic. $oe./ 

 1890, p. 114). 



128. Anilin Blue. Used alone, without special precautions, 

 this is a diffuse stain hardly to be recommended at the 

 present time. See, however, the method of HEIDENHAIN,, 

 Arch. f. mile. Anat., vi, 1870, p. 404. It is useful for double- 

 staining. 



129. Violet B. (S. MAYEE, Sitzb. d. If. k.AJcad. d. Wiss., Wien, iii Abth., 

 February, 1882). Used in solutions of 1 grm. of the colour to 300 grms. of 

 0'5 per cent, salt solution, and with fresh tissues that have not been treated 

 with any reagent whatever, this colour gives a stain so selective of the ele- 

 ments of the vascular system that favorable objects, such as serous mem- 

 branes, appear as if injected. The preparations do not keep well ; acetate of 

 potash is the least unsatisfactory medium for mounting them in. 



130. Anilin Black (Blue-black, Nigranilin, Noir de Colin). Has 



a special affinity for ganglion-cells, and is much used in the study of the cen- 

 tral nervous system. See post, Part II. 



According to CEETES, anilin black dissolved in sea or fresh water is useful 

 for the study of Infusoria, to which it is in no way toxic. 



131. Saurefuchsin (Fuchsin S., Acid Fuchsin). A f uchsin in which 

 the colouring principle is an acid, instead of being a base as in ordinary f uch- 

 sin. It is only made by the " Badische Anilin und Soda Fabrik." It may be 

 obtained from Griibler or the other providers of histological reagents. It is 

 a powerful diffuse stain, having a special affinity for axis-cylinders, and is 

 chiefly used for staining nerve-centres. See the chapter on Nerve-Centres,, 

 in Part II. 



132. Congo Red (Congoroth) (see Griesbach, in Zeit. f. wiss. Mik., iii, 

 3, 1886, p. 379). Also an " acid" colour, in the sense in which that appel- 

 lative is given to Saurefuchsin. The aqueous solution, however, has a 

 neutral or alkaline reaction. It becomes blue in presence of the least trace 

 of free acid (hence Congo is a valuable reagent for demonstrating the presence 

 of free acid in tissues ; see the papers quoted, 1. c.). A diffuse stain, much of 

 the same nature as that of Saurefuchsin, and like it seems to be at present 

 chiefly useful in staining axis-cylinders. See the chapter on Nerve-Tissue, 

 in Part II. It may also be used for staining some objects during life. Se 

 ante, 93. 



133. Benzopurpurin. According to G-riesbach (1. c.), another 

 "acid" colour very similar in its results to Congo red. It 

 is probably one of the best diffuse stains yet made known^ 

 and as a contrast stain to hasmatoxylin, will very likely take 

 the place of eosin in many cases. It is a very strong stain, 

 therefore a very weak solution should be taken, and only 

 allowed to act for a minute or so. ZSCHOKKE (ibid., v, 4, 



