460 



THE QUARTERLY REVIEW OF BIOLOGY 



the possible effect which these states 

 might exert upon the particular properties 

 being studied. Perhaps more often there 

 was a contamination with lipoid impuri- 

 ties, which invariably accompany the pig- 

 ments when they are being separated from 

 the plant or animal tissues. Not knowing 

 much about the chemical nature of the 

 pigment with which he was working, very 

 often the investigator failed to protect the 

 pigments from high temperature and from 

 oxidation. The earlier investigators did 

 not realize that some of the most charac- 

 teristic properties of the pigments they 

 were working with were subject to modifi- 

 cation even in the earlier stages of oxida- 

 tion. Often the sole basis for classifica- 

 tion of the animal chromolipoids has been 

 certain color reactions with reagents and 

 the spectroscopic properties of the pigment 

 involved. These tests are now known to 

 be insufficient for a proper classification 

 of the yellow pigments found in plants 

 and animals. The greatest confusion has 

 been in the terminology of the animal 

 pigments, but those who have been study- 

 ing the pigments of plants have often 

 proposed names already in use for pigments 

 of obviously different composition and 

 properties. It appears as if there is still 

 some confusion regarding xanthophyll. 

 Efforts at bringing order out of such a 

 chaotic condition should be welcomed by 

 all who are interested in our knowledge 

 concerning the yellow pigments whether 

 they are found in plants or animals. The 

 efforts of Thudichum, Krukenberg, Schrot- 

 ter-Kristelli, Zopf and Tswett will here 

 be reviewed. 



Thudichum (1869) was perhaps the 

 first one to attempt to bring the various 

 yellow pigments together under one name 

 ■ — "luteine" or luteins. Prior to this 

 (1866) Piccolo and Lieben had crystallized 

 the corpus luteum pigment and had called 



it luteohematoidin or hemolutein. Holm 

 (1867) isolated the corpus luteum pigment 

 and called it hematoidin. The luteins 

 which Thudichum mentioned included the 

 corpus luteum pigment, the yellow pig- 

 ment of blood serum, adipose tissue and 

 butter, and the yellow pigment of egg 

 yolk. The vegetable pigments in the 

 lutein group included the pigment of 

 yellow corn, the pigment of anatto seed, 

 pigments of the carrot root and of yellow 

 leaves and the pigments present in thei 

 stamens and petals of many flowers. 

 Thudichum's classification was never 

 widely adopted. 



Krukenberg (1886) proposed the name 

 lipochrome for all the animal and plant 

 pigments which had previously beenj 

 known as luteins, carotins, zconerythrin,i 

 tetronerythrin, chlorophan, xanthophan: 

 and rhodophan. The name lipochrome 

 has been quite widely adopted, probably 

 owing to the fact that the pigments were- 

 associated with fat in their natural state.: 

 Kohl (icpx), however, objected to calling 

 carotin a lipochrome, for it is known toi 

 occur in numerous cases quite free from 

 fat. 



A few years later, Schrotter-Kristellil 

 (1895) proposed to group together all the 

 plant and animal coloring matters which 

 had previously been known as etiolin,' 

 chlorophyll yellow, xanthin, anthoxan-- 

 thin, lutein, xanthophyll, chrysophyll, 

 carotin, phylloxanthin, phycoxanthin, 

 erythrophyll, solanorubin, lipoxanthin ,: 

 hematochrom, chlororufin, bacteriopur- 

 purin, hemolutein, vitellorubin, and tetron- 

 erythrin. These pigments he regarded as 

 an homologous group, if not completely 

 identical, and chose the name lipoxanthin 

 as a general designation. The lipoxan- 

 thins are a more or less indefinite group of 

 pigments, which may be classified just as 

 well under one head by the older term 



