Natural Dyes 213 



O— CH. 



I I 

 /\_0 

 H I I 



I 



I CH2 



CH3 0_| I N_ I 



\/\ / CU, 

 CH3O/ c 



l\ 



H OH 

 C20H15NO5; Mol. Wt. 353.360 



This compound acts as a basic dye. It has rarely been specified 

 in biological work; but Metcalf and Patton (1944) mention it as 

 a fluorochrome in connection with insect histology. 



U20 Cochineal Products c. i. no. 1139 



Cochineal is a dye that has long been well known. It is obtamed 

 from a tropical insect generally known as the cochineal insect. By 

 grinding and extracting the dried bodies of the female of the species 

 in question a deep red dye is obtained, which is known as cochineal. 

 On treatment with alum this solution yields a product somewhat 

 more free from extraneous matter, known as carmine. This is the 

 form in which the dye is generally obtained by the microscopist. 

 Cochineal products are used in various ways in microscopic technic, 

 generally as nuclear dyes. They are extremely valuable in cases 

 where it is desirable to stain in bulk before sectioning. 



Cochineal, itself, has been used for various purposes in micro- 

 scopic technic, even though less used today than carmine. Alone it 

 has little value, to be sure, for it has no direct affinity for tissues un- 

 less they contain iron, aluminium or some other metal. It is most 

 commonly employed either with or following a salt of one of these 

 metals as a mordant. A tincture of cochineal, that is an alcoholic 

 solution containing calcium and aluminium chlorides, has been 

 used by Mayer (see Lee, 1937, p. 149) both on sections and for 

 staining in bulk; but its most common method of use is with alum 

 in watery solution. An alum-cochineal of this sort was first used 

 independently by Mayer (1878, 1892) and Czokor (1880); it can 

 be used for sections, and is specially recommended for staining in 

 bulk, by which technic it stains nuclei violet red, and blood and 

 muscle cells orange, while the cytoplasm is but weakly colored. 

 A chrom-alum-cochineal has been used by Hansen (1905) for stain- 

 ing sections. Spuler (1901) recommends an iron-alum-cochineal 

 for staining in bulk when the sections are to be photographed, the 

 technic bringing out nuclei, the blood in the tissues, and the muscle 

 striations; sections may also be stained by the same method. By 



