186 NUCLEAR STAINS, COAL TAR 



of the bodies that have been described as " eoccidia," " sporozoa," or 

 other ■' parasites "" of carcinoma are nothing but particles of this 

 precipitate. 



See also the differentiation process of Martinotti and Resegotti 

 (Zeit. zviss. Mik., iv, 1887, p. 328) for alcohol-fixed material, and of 

 Garbini {Zeit. zviss. Mik., v, 2, 1888, p. 170). 



In preparations made with chromo-aceto-osmic acid, safranin 

 stains, besides nuclei, elastic fibres, the cell bodies of certain 

 horny epithelia, and the contents of certain gland-cells (mucin, 

 under certain imperfectly ascertained conditions). 



The stain is perfectly permanent. 



373. Gentian Violet* may be used in aqueous solution, or as 

 directed for safranin. This stain is now being much used for 

 chromosomes. Solubility at 26° C, in water 2-93 per cent., in 

 alcohol 15-21 per cent, (crystal violet). 



In some cases it may be useful to employ the method devised 

 by Gram for the differentiation of bacteria in tissues {Fortschr. 

 d. Medicin., ii, 1884, No. 6 ; British Med. Jour., September 6th, 

 1884, p. 486 ; Jour. Roy. Mic. Soc. [N.S.], iv, 1884, p. 817). In 

 this the sections are treated, after staining, with a solution com- 

 posed of — 



Iodine ...... 1 grm. 



Iodide of potassium .... 2 grm. 



Water 300 „ 



for two or three minutes, until they become black. They are 

 then differentiated with neutral alcohol, until they turn grey, 

 and are then finally differentiated with clove oil. 



By this process, in resting nuclei the nucleoli alone are stained, 

 or the chromatin if stained is pale ; in dividing nuclei the chromatin 

 is stained with great intensity, being nearly black in the equatorial 

 stage. 



Gentian violet is an exceedingly powerful stain, quite as precise 

 as safranin. 



The stain keeps well. It is more or less dichroic, possibly 

 owing to the fact that the dye is not a pure substance, but a 

 mixture of " Krystallviolett " and methyl violet. 



According to Conn {op. cit.) one should specify " crystal violet " 

 for bacteriological work, or histological work where a deep blue- 

 violet is required, or methyl violet 2 B, where in histology a 

 reddish shade is wanted. The American Commission on Stains 

 proposes to drop the term " Gentian Violet " at some later 

 period. 



Hermann {Arch. mik. Anat., xxxvi, 1889, p. 58) first stains for twenty- 

 four hours or more in safranin, differentiates incompletely with alcohol, 

 then stains for three to five minutes in the anilin-water gentian solution, 

 treats with the iodine solution for one to three hours, and finally 

 differentiates with absolute alcohol. 



* Refer especially to § 1364- 



