COAL-TAR PLASMA STAINS. 213 



It should be borne in mind that picric acid has consider- 

 able power of crashing out other anilin stains ; and that in 

 combination with hydrochloric (<'<! it very greatly enhances 

 the power with which this acid washes out carmine stains. 

 It should, therefore, not be added to the acidulated alcohol 

 taken for differentiating borax-carmine stains, or the like, 

 but only to the neutral alcohol used afterwards. It has the 

 great quality, shared by very few plasma stains, that it can 

 be used for staining entire objects. And as it is extremely 

 penetrating, it is very much indicated for the preparation of 

 such objects as small Arthropods or Nematodes, mounted 

 whole. 



It can in some cases be employed by dissolving it in the 

 solution of another dye (see Picro-carmine, LEGAL' s alum- 

 carmine, 216, etc.) ; or (for sections) by dissolving it in the 

 xylol or chloroform used for clearing. 



282. Orange G. This is the benzenazo-beta-naphthol- 

 disulphonate of soda (to be obtained from Griibler & 

 Hollborn, and not to be confounded with about a dozen 

 other colours that are on the market under the name of 

 t( Orange/' with or without a suffix). As indicated by its 

 chemical description, this is an " acid " colour in Ehrlich's 

 sense ; and according to FLEMMING (Arch. mik. Anat., xxxvii, 

 1891, p. 685) it is also an acid colour in the usual sense, its 

 solution in water having an acid reaction. My sample, 

 however, obtained from Griibler & Hollborn, and stated 

 to be identical with that supplied to Flemming, shows no 

 sign of an acid reaction. MAYER has examined two samples, 

 with the same result. Probably Flemming's sample was 

 not pure. The solutions do not keep well, throwing down 

 very quickly a pulverulent deposit. 



I think this is one of the most precise cytoplasm stains 

 that I have met with, but the stain is a very pale one. I 

 use a saturated solution in water, and allow it to act for five 

 or ten minutes (sections only). 



283. FLEMMIXG'S Orange Method (Arch.f. mik. Anat., xxxvii, 1891, 

 p. 249 ; ibid., p. 685 ; Zeit. f. wise. Mik., viii, 2, 1891, p. 223, and viii, 3 

 p. 343). Stain (for as much as two or three days, or even weeks if you 

 want a very powerful stain) in strong alcoholic safranin solution diluted 

 with anilin water ( 272) ; rinse in distilled water ; differentiate in absolute 



