CHAPTER XXXI 

 VITAL STAINING * 



PART I. GENERAL AND THEORETICAL 



739. Types of Staining. Vital staining is the technique of 

 colouring living cells. This may be brought about by the staining 

 of preformed structures, by a general diffuse staining, or by the 

 deposition of dyestuff as new intracellular formations (segregation, 

 or " Speicherung "). Recent work has indicated that the type of 

 staining is dependent to a certain extent upon the state of 

 functional activity of the cells. 



740. Vital Stains. Almost all the dyes employed for vital 

 staining belong to one or other of the classes of acid or basic 

 dyes. Acid dyes may be considered as salts of colour acids with 

 bases, usually Na, K, or Ca ; and basic dyes as salts of colour 

 bases with acid radicles, usually — CI or — SO4. The following 

 are the dyestuffs most frequently employed in vital staining : — 



Acid Dyes. Trypan blue, trypan red, vital new red, isamine 

 blue (pyrrol blue). 



Basic Dyes. Neutral red, Janus green, brilliant cresyl blue, 

 methylene blue and Bismarck brown. 



Most acid dyes are water soluble, but insoluble in lipoid solvents. 

 The majority of basic dyes, while soluble in water, have a certain 

 degree of lipoid solubility. 



741. General Methods of Staining, f Small aquatic animals can 

 be stained by the addition of dyestuffs to the water in which they 

 are kept. Terrestrial animals are injected with dilute solutions, 

 the more diffusible dyes being injected subcutaneously or intra- 

 peritoneally, and the less diffusible intravenously. These methods 

 are usually described as intra vitam staining, or staining in vivo. 

 Staining of teased tissues, or isolated cells in dilute dye solutions, 

 is known as supra vital staining, and is the method usually 

 employed with basic dyes. One of the best means of studying 

 vital staining is to employ tissue cultures — vital staining in vitro. 

 Special irrigation apparatus for bathing cells with dye solutions 

 has been devised by some workers (see Nagel, Zeit.f. Zellforsch., 

 ix, 1929, p. 346). 



742. Vital Staining by Segregation, The acid dyes employed 

 for vital staining, on entering living cells, are segregated as 



t For Simpson's coverslip method, see § 872. * By R. J. L. 



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