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



with these properties of the retinal pigments. A study of their spectro- 

 scopic absorption properties led him to believe that the pigments were 

 not identical. 



Kiihne in his celebrated work on "Optochemie" occupied himself 

 somewhat again with the egg yolk pigment and called it Ontochrin 

 or Lecithochrin. He did not try to isolate it free from nitrogen, but 

 he did succeed in observing crystals. He again was careful to dis- 

 tinguish between the egg yolk pigment and the corpus luteum pigment, 

 which he at this time considered as extraordinarily closely related to 

 carotin. 



The Lipochromes. Basing his work on the researches of Kiihne, 

 Krukenberg commenced a series of researches which extended from 

 1879 to 1886, the most important of which appeared in his "Verglei- 

 chende Physiologische Studien" * and especially in the paper, "Grund- 

 zuge einer vergleichenden Physiologic der Farbstoff und der Farben' r 

 which appeared in 1884. Krukenberg made an exhaustive study of 

 what had been done on animal pigmentation and included under one 

 head all those pigments which had previously been known as luteins, 

 carotin, zoonerythrin (tetronerythrin) and Kiihne's chromophanes, and 

 called them lipochromes. 



Krukenberg believed that carotin, the pigment of the carrot, was 

 the best representative of the lipochrome coloring matters, and ac- 

 cepted Husemann's formula for carotin (C 18 H 24 O) as representing 

 the chemical composition of the lipochromes. 



In regard to the origin of lipochromes Krukenberg believed, "It 

 is probable that in most cases they originate from fatty substances, 

 for frequently, if not without exception, they occur in company with 

 fat and allow themselves to easily go over into cholesterin-like bodies." 



In 1885 Krukenberg 2 isolated a yellow lipochrome from the blood 

 serum of the ox by extracting the serum with amyl alcohol. The 

 solution showed two absorption bands, one enclosing the line F and 

 the other lying between F and G. A year later Halliburton 3 reported 

 that he extracted a yellow lipochrome from the blood serum of the 

 pigeon, hen, dove and tortoise by means of alcohol. Halliburton re- 

 ported an identical pigment in the body fat of these same animals. 



MacMunn 4 was the next investigator of animal pigments, and 

 like Krukenberg, he extended the classification lipochrome to include 



1. Zoonerythrin (Tetronerythin) : Central, f. d. Medic. Wiss. 1879. Vergl. 

 Physiol. Studien I Reihe, II Abth. s. 67-71; III Abth. s. 114-115; IV Abth. s. 

 30-35; V Abth. s. 87-94; II Reihe, I Abth. s. 165-167; III Abth. s. 135). 



2. Sitz, ber. d. Jen. Gessel. f. Med. 1885. 



3. Jour. Physiol. 7, p. 324 (1886). 



4. Philos Trans. Roy. Soc. 177, p. 247 (1886). 



