THE PIGMENTS OF ORGANISMS 39 



4. Reserve Products 



The nejit group of pigments includes those which 

 are actually reserve products or are associated with 

 such. Although the literature of the subject contains 

 numerous mention of pigments described as reserve 

 products, it is still doubtful whether the description 

 is accurate in any one of the cases. Carminic acid, 

 the pigment of the coccus insect, is very frequently 

 described as a reserve, but this is doubtful ; it is a 

 glucoside, and therefore a carbohydrate is produced 

 by boiling it with dilute acid, but nothing is certainly 

 known as to its function. 



The term reserve product is applied with more 

 plausibility to various members of the large series of 

 lipochromes or fat-pigments. The lipochromes are 

 pigments, varying from yellow through orange to red 

 in colour, which in the dry state give a blue colour 

 with concentrated sulphuric or nitric acid, and which 

 are soluble to a greater or less degree in all the 

 solvents of fats, as well as in fats themselves. They 

 are divisible into two series, according as they do or 

 do not form compounds with the caustic alkalies. 

 Both series occur in animals, but the second only in 

 plants. In plants the best known lipochrome is 

 carotin, which is widely distributed, and is, according 

 to Carl Ehring, a cholesterin fat. The chemical 

 nature of the other series is still unknown. 



The lipochromes occur frequently, though not 

 invariably, in association with fat in organisms. 

 From the red flesh of the salmon, for example, it 

 is possible to extract an oil containing the pink 



