GENERAL DISTRIBUTION OF CAROTINOIDS 



constitution is unknown, but which is thought to be derived from the 

 blood corpuscles, is hiimatoidin, a yellow crystallizable pigment found 

 in old blood c-xudates, in mummified embryos, and sometimes in the 

 urine and other excreta. First described and named by Virchow 

 (1847) and later by others, its origin as well as chemical properties 

 and crystalline form have been recently studied anew by Neumann 

 (1904, 1905). Holm (1807) thought the corpus luteum pigment was 

 hiimatoidin in his early study of this pigment which has since been 

 shown to be carotin. 



Another much more widespread yellow animal pigment with cer- 

 tain lipochrome properties is the bile pigment bilirubin. There is 

 less danger of confusing it with carotinoids, however, save with respect 

 to its color, inasmuch as it is a nitrogen containing substance which 

 readily forms salts with the alkali and alkaline earth metals, and has 

 many other properties at variance with those of the carotinoids. 



Other non-carotinoid pigments exist in animal tissues, but which 

 resemble the carotinoids in color and in solubility in fat solvents. 

 Palmer and Kempster (1919 a ) have recently encountered such a pig- 

 ment in the carotinoid-free egg yolks of hens raised from hatching on 

 rations devoid of carotinoids, the eggs being produced likewise on 

 xanthophyll-free rations. The small amount of pigment found in the 

 yolks could be extracted by acetone, but hardly at all by ether, was 

 almost entirely saponifiable and failed to respond to characteristic 

 xanthophyll tests. The author finds that a similar pigment can be 

 extracted from the carotinoid-free and apparently colorless "corpus 

 luteum" of the sow, if a sufficient number of these organs are mac- 

 erated and extracted with fat solvent. These cases are cited in order 

 to point out the danger in assuming that all animal pigments of a 

 yellow color are carotinoid in nature. Such a sweeping conclusion 

 cannot be justified. 



The same statement can also be made, although with less assur- 

 ance, for certain red pigments which appear among the lower animals 

 and birds. These pigments, as indicated, are red in the solid condition 

 but their dilute solutions are usually yellow. They have been studied 

 by certain of the older investigators, such as Kiihne, Maly, Kruken- 

 berg, MacMunn and Zopf and others, and have received various 

 names at the hands of these authors, such as rhodophan, vitellorubin, 

 crustaceorubin, tetronerythrin, lina-carotin (from the Lina species of 

 beetles in which they occur) and diaptomin. The pigments are strik- 

 ingly similar in many respects to the carotinoids, but differ from them 



