20 CAROTIN VIDS AND RELATED PIGMENTS 



word form cannot be restricted to crystalline form, inasmuch as the 

 crystalline form of the carotinoids varies widely depending upon the. 

 solvent from which they separate. As will be pointed out later, how- 

 ever, the carotinoids must of necessity be closely related structurally. 

 Their close chemical relations and the fact that they are invariably 

 found together in chlorophyllous organs support this view. 



Tswett's terminology has given promise of presenting a very simple 

 solution of the difficulties of nomenclature in connection with the vari- 

 ous red and yellow tinted pigments which conform to the properties 

 of the so-called lipochromes so widely distributed in all forms of plant 

 life. Unfortunately, however, Lubimenko (1914, 1915, 1916) has 

 greatly complicated the system on very inadequate evidence by using 

 the ending -oid for a group of pigments which he believes to corre- 

 spond to each of the definitely known carotinoids. Thus, Lubimenko 

 speaks not only of carotin, xautliophyll, lycopin, etc., but of caro- 

 tinoids, xanthophylloids, lycopinoids, etc., as well. One cannot but 

 express the opinion that our knowledge of the carotinoids in the sense 

 used by Tswett, and followed in this monograph, is not sufficiently 

 extensive to warrant a belief in the existence of numberless interme- 

 diate products. As a matter of fact, the chemistry of the specific indi- 

 viduals of Lubimenko's terminology, namely carotin, lycopin, xantho- 

 phyll and rhodoxanthin, argues against the existence of many plant 

 chromolipoids of the nature of those mentioned. Certainly in view 

 of the fact that there is every evidence to believe that all the xan- 

 thophylls bear the simple relation to carotin that is expressed in their 

 respective formulae, C 40 H 56 and C 40 H 56 O 2 , it seems little short of pre- 

 posterous to assume the existence of a group of "carotinoids" which 

 are oxidation products of carotin and another group of "xanthophyl- 

 loids" which are reduction products of xanthophylL 



Tswett's terminology, therefore, seems entirely adequate for our 

 present knowledge of the chromolipoids of plant origin. If the chemi- 

 cal and physiological relation of the carotinoids to the yellow animal 

 chromolipoids of the tissues and fluids of the higher mammals and 

 man, and of the egg yolk and bodies of oviparous animals, is a cri- 

 terion of similar relations throughout the entire realm of the animal 

 kingdom, then Tswett's terminology is equally applicable to the 

 yellow and red tinted chromolipoids so widely distributed in all forms 

 of animal life. The probability of such a relationship is, in fact, the 

 basis of the present monograph. 



