188 CAROTINOIDS AND RELATED PIGMENTS 



Somewhat more convincing were Sauerraann's results on feeding the 

 red pepper to laying hens. By feeding a hen 5 grams of the pepper 

 each day the pigment appeared in the third egg laid after the beginning 

 of the pepper feeding, as a thin band of color at the periphery of the 

 yolk. By the time the sixth egg was laid the yolk was entirely pig- 

 mented. Two interesting properties were noticed in connection with 

 the yolks colored by the pepper pigment: (1) it was impossible to 

 hard-boil them, (2) ether would not extract all the color from the dried 

 yolks, because a part of the pigment was apparently bound tightly to 

 the protein. 



These experiments have a bearing on the biological relationship be- 

 tween plant and animal carotinoids for two reasons. They not only 

 record the first authentic instance in which a plant carotinoid was 

 transferred to an animal under experimental conditions, but are also 

 the only experiments showing the possibility of lycopin occurring in 

 the animal body. It was shown in Chapter II that the evidence indi- 

 cates that the chief pigment in the ripe fruit of the pepper plant, 

 Capsicum annum, is the red carotin isomer, lycopin. Presumably this 

 was the chief pigment in the cayenne pepper which Sauermann fed to 

 his hens, and which appeared in the egg yolks and in the feathers in 

 two of the birds. The evidence, although circumstantial, is strongly 

 in favor of this deduction, and should be submitted to further verifi- 

 cation because the result presents the apparent anomaly that lycopin, 

 the isomer of carotin, can be transferred abundantly to the egg yolk 

 of the hen while carotin appears in the yolk only in traces even under 

 the most favorable conditions: 



The next experiment was that of Poulton (1893), carried out to 

 verify his previous (1885) hypothesis that the colors of caterpillars 

 are due largely to plant pigments derived from the food. Newly 

 hatched larvae were placed on three diets: (1) yellow etiolated leaves 

 from the center of a heart of cabbage, (2) white mid-rib of cabbage 

 containing no pigment, and (3) deep green external leaves. All were 

 kept in the dark. The larva? raised on the green leaves and the 

 etiolated leaves grew normally, those on the etiolated leaves growing 

 far more rapidly than those on the green leaves. Both of these sets of 

 caterpillars developed the normal green and brown colors of the 

 species. The caterpillars on the colorless cabbage did very poorly and 

 only one was raised to adult size. This individual, however, remained 

 colorless throughout the experiment. Some of the group of caterpillars 

 on the colorless food were placed on the etiolated leaves after growing 



