CAROTINOIDS IN THE VERTEBRATES 149 



chrome point of view have been confined to the frog and salamander. 



The alcohol and ether cxtractability of the yellow pigment in frogs 

 was known to the early observers, such as v. Wittich (1854), Leydig 

 (1868), Bering and Hoyer (1869), before Capranica (1877) found 

 that the retinal pigment of the frog corresponded in its general solu- 

 bility, chromatic and spectroscopic properties with the corpus luteum 

 and egg yolk pigment. Kiihne's (1878) chromophane studies included 

 the pigment in the retinal and adipose tissue of frogs, as well as the 

 skin. Only one pigment was found, readily and completely extract- 

 able from the saponified extracts with petroleum ether. On account 

 of a slight spectroscopic difference from the pigment of egg yolk 

 (absence of a faint third band in spectrum of frog pigment) Kiihne 

 gave the frog pigment the name lipochrin. 



Krukenberg (1882c) repeated Kiihne's work on the yellow or orange 

 skin pigment of the frogs Hyla arborea, Rana esculenta, the toads 

 Bufo viridis, Bufo calamita, Bufo vulgaris, and the orange skin pig- 

 ment of the salamanders, Triton cristatus and Salamdra maculosa. 

 The same pigment was found throughout, also in the ovaries of 

 B. calamita and the fatty tissue of Triton cristatus. A comparison of 

 the spectral drawings of Kiihne and Krukenberg for their amphibian 

 lipochromes shows certain differences in the positions of the absorption 

 bands such that it is impossible to decide whether the pigment is 

 carotin or xanthophyll, so that the determination of this important 

 point will have to be left to future investigation. It should be stated, 

 perhaps, that Magnan (1907a, b) has claimed to have isolated a green 

 and a yellow pigment from several Batracian's skins, the yellow pig- 

 ment differing from the chromolipoid obtained by previous workers 

 in that it failed to show absorption bands, and was soluble in NaOB 

 and KOH. One cannot help but raise some doubt as to the accuracy 

 of this worker's observations both as to the properties of his yellow pig- 

 ment and the existence of a green pigment. It is an old observation 

 that the frog skin loses its green color on extraction of the yellow 

 pigment, showing that the green color is partly of pigment and partly 

 of structural origin. 



Carotinoids in Reptiles 



The surface colorations of reptiles are perhaps even more conspicu- 

 ous than those of amphibians. The lizards and snakes have been 

 studied most, and there has been at least one observation regarding 

 lipochromes in turtles. The deposition of the skin pigment in nerve 



