74 DIRECT NUCLEAR STAINS. 



ence of methyl green and Bismarck brown is a sufficient reason for being 

 silent, in this connection, with regard to the rest. 



109. Methyl Green. This is the most common in commerce, 

 of the " anilin " greens. It appears to go by the synonyms 

 of Methylanilin green, Vert Lumiere, Lichtgriin, Griinpulver. 

 When first studied by Calberla, in 1874 (Morphol. Jahrb., iii, 

 1887, p. (325), it went by the name of Vert en cristaux. It is 

 commonly met with in commerce under the name of more 

 costly greens, especially under that of Iodine green. It is im- 

 portant not to confuse it with the latter, nor with Aldehyde 

 green (Vert d'Eusebe), nor with the phenylated rosanilins, 

 Paris green, and Vert d'alcali or Veridine. 



The chief use of methyl green is as a nuclear stain for fresh 

 or recently fixed tissues. For this purpose it should be used in 

 the form of a strong aqueous solution containing a little acetic 

 acid (about 1 per cent, in general). The solutions must always 

 be acid. (One of the latest books on the subject I have 

 seen gives a formula for a methyl green solution for 

 staining nuclei in which no acid is mentioned. Such a solu- 

 tion would not give the pure nuclem reaction which it is the 

 special function of this reagent to produce.) You may wash 

 out with water (best acidulated) and mount in some acid 

 aqueous medium containing a little of the methyl green in 

 solution. The mounting medium, if aqueous, must be acidu- 

 lated. 



Employed in this way, methyl green is a pure nuclear stain, 

 in the sense of being a precise colour-reagent for nuclein. 

 For in the nucleus it stains nothing but the chromosomes, or 

 nuclein elements : it does not stain either nucleoli of any sort, 

 nor caryoplasm, nor achromatic filaments. Outside the nucleus 

 it stains some kinds of cytoplasm and some kinds of formed 

 material, especially glandular secretions (sericin, for instance). 

 But the nuclein elements are invariably stained of a bright 

 green (with the exception of the nuclein of the heads of some 

 spermatozoa), whilst extra-nuclear structures are in general 

 stained in tones of blue or violet. 



The following paragraph, translated from the paper by Calberla above 

 quoted, appeared inadvertently without comment in the first edition, and has 

 since been repeated without comment in several places. 



" He then found that ' the nuclei of subcutaneous connective tissue and 



