PHYSIOGENESIS. 239 



' * That the yellow color of canaries can be altered 

 to an orange red by mixing cayenne pepper with their 

 food, has been known for a long time. This curious 

 fact was first discovered in England, as was also the 

 fact that the different races of canaries vary in their 

 susceptibility to the action of the pepper ; some kinds 

 are more, others are less, affected, while one race is 

 absolutely without any power of having its coloration 

 altered by these means. The color-change is pro- 

 duced by feeding the newly hatched young with the 

 pepper conveyed in their food or the old birds while 

 sitting upon the nest are furnished with food contain- 

 ing the cayenne, which they in turn feed their offspring. 

 The color change can, in fact, be only brought about 

 in very young birds whose feathers are not completely 

 matured ; it is quite impossible to produce any altera- 

 tion upon the full-grown canary. Clearly, therefore, 

 here is an instance of the direct effect of food upon 

 color. An interesting paper upon the subject, which 

 has also furnished me with the facts already men- 

 tioned, has lately appeared, 1 and it will be of interest 

 to give some account of the author's (Dr. Sauermann's) 

 experiments for reasons that will appear. Cayenne 

 pepper, of course, is a composite substance, from which 

 a number of distinct chemical substances can be ex- 

 tracted : the red color is caused by a pigment termed 

 capsicin, which can be separated from the pepper ; 

 and it might easily be supposed that the change from 

 yellow to red in the feathers of the canary was simply 

 caused by a transference of the pigment, as in the 

 cases mentioned on page 127; but Dr. Sauermann 

 shows that it is not so. Yellow-colored canaries were 



\Archiv fur Anatotnie und Physiologic. 1889. Physiologische Abtheilung, 

 543- 



