138 CHAPTKIt XT. 



FISCHEL (Anat. Hcfle, xvi, 1901, p. 417, and op. cit. supra) 

 concludes in favour of the vitality of certain of the stained 

 granules. 



Apart, however, from this question, it must be conceded 

 that these so-called " vital stains" are frequently very useful. 

 According to my experience, methylen blue is the most 

 generally useful of them. It has (with Bismarck brown, 

 Congo red, and neutral red) the valuable point that it 

 is sufficiently soluble in saline solutions, and may therefore 

 be employed with marine organisms by simply adding it 

 to sea-water. The others are not thus soluble to a practical 

 extent, but I find that gentian and dahlia become so if 

 a trace of chloral hydrate 0'25 per cent, is ample enough 

 be added to the saline solution. Any of these reagents 

 maybe rubbed up with serum, or other " indifferent ' liquid. 



Methylen blue may be fixed in the tissues, and permanent 

 preparations made, by one or other of the methods described 

 in Chap. XVI. Bismarck brown stains may be fixed with 0'2 

 per cent, chromic acid or with sublimate solution (MAYER), 

 or 1 per cent, osmic acid (LoisEL, Journ. de I'Anat. et de la 

 Phys.j 1898, No. 2, p. 212 a work that contains a good deal 

 of information on the subject of intra-vitam stains), and the 

 preparations may be stained with safranin, care being taken 

 not to expose them too long to the action of alcohol. For 

 the study of cell-granules, neutral red is perhaps the best. 



FISCHEL (" Unters. ueb. vitale Faerbungen," Leipzig. 

 1908) finds that alizarin is specific for nerves. Add excess 

 of alizarin to boiling water, boil and filter, and add 1 vol. of 

 the filtrate to the water containing the organisms (Cladocera). 

 The stain takes several hours. 



For sulphorhodamin, which is selective for many organs 

 (kidney, liver, uterus, skin, lymph-glands, etc.), see 

 ANDREEW, in Virchow's Arch., cciv, 1911, p. 447. 



See also GOLLMAN, Proc. Roy. /SV., Ixxxv, 1912, p. 146 

 (trypan blue, i sain in blue, diamin blue, etc.) ; and GOLDMANN, 

 " Die aeussere u. innere Sekretion, etc./' TUBINGEN, 1909, 

 and " Neue Untersuch., etc.," ibid., 1912. 



209. The Practice of Staining. Selective staining is arrived 

 at in two ways. In the one, which is called the progressive 

 nii'thod, you make use of a colouring reagent that stains the 



