332 VITAL STAINING 



vacuoles and granules are those which, while water soluble, are 

 only slightly soluble in lipoids, but are readily flocculated in 

 contact with acid colloids, e.g. neutral red. Seki {Zeit. f. Zell- 

 forsch., xix, 1933, p. 289) also concludes that an intense granular 

 staining depends essentially upon a reciprocal precipitation 

 between acid substances in the watery phase of the cell granules, 

 and the basic dyestuff . Probably because of their lipoid solubility, 

 basic dyes such as neutral red, and brilliant cresyl blue readily 

 penetrate all types of cells and quickly stain cytoplasmic vacuoles 

 and granules. Also they stain yolk granules in embryonic tissues 

 and dye droplets formed as the result of vital staining with acid 

 dyes (von Mollendorff, loc. cit., 1921). Gatenby reports that 

 in germ cells neutral red stains the y-granules (rubrophile granules) 

 in insects, annelids and mammals, and the proacrosome in many 

 insects. In human spermatocytes needle-shaped crystals are also 

 stained (Gatenby, Anat. Bee, xlviii, 1931, p. 121). 



745. Segregation of Basic Dyes. Besides staining preformed 

 structures, basic dyes may under certain conditions give rise to 

 new cytoplasmic formations. Chlopin {Arch. e.vpL Zellforsch., iv, 

 1927, p. 462) has shown that with intense staining, newly formed 

 dye droplets contain varying amounts of a substance, which he 

 regards as protein from the way in which it is retained after 

 fixation. This substance he caUs the " Krinom." In fixed tissues 

 it can be stained with basic anilin dyes. 



LuDFORD (Proc. R.S.B., cviii, 1931, p. 270) demonstrated that 

 both acid and basic dyes when injected into the living animal are 

 segregated in the liver cells in the same manner, in the same region 

 of the cells, next to the intercellular bile canaliculi. He has 

 therefore concluded that a basic dye such as neutral red on 

 entering a cell is flocculated at the surface of any droplets and 

 granules that may be present, possibly only if they are of a more 

 acid character. Excess of the dye then becomes deposited as new 

 cytoplasmic formations {Biol. Bev., viii, 1933, p. 357). When 

 working with basic dyes it is essential to bear in mind the possi- 

 bility that coloured droplets which appear in cells may have been 

 induced by the presence of the dyestuff, and not have been 

 preformed. Failure to recognise this possibility has led to faulty 

 conceptions of cytoplasmic structure. 



746. Diffuse Staining of Cells. Certain basic dyes stain living 

 cells diffusely. According to von Mollendorff {loc. cit., 1920) 

 these are readily soluble in lipins, but show no disposition to be 

 flocculated by acid colloids. Some have been found neither to 

 stain preformed structures, nor to be segregated (Ludford, loc. 

 cit., 1931). Others, which are flocculated to a slight extent, stain 

 cefl granules faintly, and at the same time stain the cytoplasm 

 diffusely. The following dyes have been employed for vital 

 staining :— 



