CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT. 317 



corpus luteum pigment, the body fat pigment, and the blood serum 

 pigment; and (2) to show the chemical and physiological relation of 

 the butterfat pigment to the carotin and xanthophylls of green plants. 

 In the secondary part of the investigation it was sought to study 

 the influence of certain factors which have both practical and scientific 

 bearing upon the color of the butterfat, among which are the breed 

 of the animal and the character of the ration, the latter in connection 

 with the chemical and physiological studies indicated above. 



THE PIGMENTS OF PLANT ORIGIN. 



The earliest researches on plant pigments dealt with the green 

 pigments. Caventon first called them chlorophyll in 1817. His work, 

 however, was preceded by the pioneers in this field, among which the 

 names of Grew, whose work is dated 1682, and Rouelle, Meyer, 

 Fourcroy, Berthellot, Senebier, Proust and Vanquelin are of historical 

 interest. 



The Carotins. 



The Pigment of the Carrot. The yellow pigment of the cultivated 

 carrot (Daucus Carota) has long been of interest to botanists and 

 chemists, the investigations of this body having extended over almost 

 one hundred years. 



Wachenroder 1 was the first investigator of the carrot pigment. 

 He isolated it and called it Karotin. The work of Vanquelin and 

 Bouchardat 2 soon followed and a little later Zeise 3 took up the study. 

 He obtained the first crystals and assigned to them the chemical formula 

 C 5 H 10 or 10 (C 5 H 8 ). 



Husemann 4 was the next investigator. He found six per cent 

 of oxygen in his pure preparation and gave the pigment the formula 

 C 18 H 24 O. A secondary pigment which he thought always accom- 

 panied the carotin in small amounts, he named hydrocarotin and gave 

 it the formula C 18 H 30 O. 



It is to Arnaud 5 however that we are indebted for the first 

 thorough research in regard to the carrot pigment carotin. The crys- 

 tals which he obtained were flat, rhombic-shaped crystals, red orange 

 by transmitted light, and greenish blue by reflected light. They melted 

 at 168 C. He showed beyond a doubt that the pigment was simply 



1. Dissertatio de Anthelminticis Gottingen 1826 ; also Geigers Magaz. Pharm. 

 33 p. 144 (1831); also Berzelius Jahresber. 12 p. 277 (1833). 



2. Schweizg. Jour. Chem. 58, p. 95 (1830). 



3. Lieb. Ann. 62 p. 380 (1847); Annal. Chem. Phys. (3) 20, p. 125 (1847). 



4. Lieb. Annal. 117 p. 200 (1860). 



5. Compt Rend. 102 p. 1119 (1886), p. 1319 (1887); Jour. Pharm. Chim. 

 14 p. 149 (1886). 



