332 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN No. 9. 



of heat, the milk fat showed an intense blue coloration. The feces, 

 however, showed the pigment in an unchanged condition. 



Summary. 



The foregoing review of the literature has shown that the great 

 number of pigments that exist throughout the entire plant and animal 

 kingdoms have long been of interest from a scientific standpoint. The 

 pigments of botanical origin have been thoroughly and exhaustively 

 investigated. This is especially true of the yellow pigments carotin 

 and xanthophylls, and their chemical constitution and properties are 

 now established. 



The yellow and orange pigments of plants were at first classified 

 in one group, and were called carotins, the name being derived from 

 the pigment of the carrot, which was the first one investigated. A 

 great many different names were given to this pigment as it was 

 independently discovered in various plants but the identity of these 

 pigments with the carrot pigment has now been established. It was 

 eventually discovered that the carotins are always accompanied, especi- 

 ally in green plants, by a second great class of pigments which have 

 been called xanthophylls, whose relation to carotin has but recently 

 been established. 



As the work on plant pigmentation developed, it was recognized 

 that the general properties of a great many yellow pigments found in 

 animals were similar to the so-called carotins. The first investigators 

 classified these animal pigments under the name lutein, the name 

 being derived from the pigment of the corpus luteum, which was the 

 first one investigated. The name lutein was extended by the animal 

 chromotologists to include the carotins of plants and its related pig- 

 ments. Later, when the animal luteins had become generally recog- 

 nized by their association with fat, the name lutein was changed to 

 lipochrome and this designation was also extended to include all sim- 

 ilar pigments of both plants and animals. 



The classification of the plant and animal pigments which is at 

 present generally accepted is to restrict the names carotin and xan- 

 thophylls to the two great classes of yellow plant pigments, and to 

 include under the name lutein or lipochrome only those yellow pig- 

 ments which are considered to be of animal origin. 



The most recent work in the field of animal chromotology has 

 shown that the luteins can also be subdivided into carotin and xan- 

 thophyll groups depending on their chemical relation to the carotin or 

 xanthophylls of plant origin. Accordingly Schunck l has shown the 



1. Loc. cit. 



