106 



Biological Stains 



The dye, thionin, is a salt, generally a chloride, of the above- 

 mentioned base; and on the assumption of paraquinoid structure, 

 it has the following formula: 



ILN 



\/~N=\/ 

 C12H10N3SCI; Mol. Wt. 263.741 



{A basic dye; absorption maximum 598-599.) 

 Solubility at 26°C: in water 0.25%; in alcohol 0.25% 



Thionin is violet in dilute solution, and has a very pronounced 

 metachromatic effect, the colors in sections stained with it ranging 

 from blue to reddish violet. A spectrophotometric graph of a 

 typical sample of thionin is given in Fig. 11, p. 105 (curve 2). 



It is no longer used as a textile dye, and is to be distinguished 

 from thionin blue (C. I. No. 926) which is known to the trade and 

 has sometimes been furnished in place of the desired dye when 

 thionin has been ordered. Thionin is an especially valuable dye 

 for histological work on account of its metachromatic properties, 

 that is, its ability to impart different colors to different histological 

 or cytological structures. It is a very valuable chromatin and 

 mucin stain, proving especially useful in staining the tissue of 

 insects; and is recommended by Ehrlich because it stains amyloid 

 blue but mast cells and mucin red. It is a useful vital stain. 

 Perhaps its greatest value at the present time is in the staining of 

 frozen sections of fresh animal or human tissue, particularly in the 

 study of tumors. It is also used by Frost (1916) for staining very 

 young bacterial colonies in his "little plate" technic for counting 

 bacteria. (Unfortunately Frost specified thionin blue in one of his 

 papers, although the latter proves entirely unsatisfactory for the 

 purpose.) 



PROCEDURES RECOMMENDED BY THE COMMISSION IN WHICH THIS STAIN IS USED' 



NAME OF PROCEDURE 



Staining frozen sections 



Staining fixed tissue 



End point staining of Nissl granules 



Schmorrs method for staining bone sections 



Stoughton's technic (with orange G) for fungi in plant tissue 



page reference to 

 Staining Procedures 



IA4-I8 

 IA4-I9 

 IC3-U 

 ID3-I2 

 IIA-12 



*Under this heading are given references to procedures described in detail in 

 Staining Procedures, edited by Conn and Darrow (194.3-52). 



