1893.] Recent Literature. 373 
birds whose feathers are not completely matured ; it is quite impossi- 
ble to produce any alteration 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 mentioned,’ 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 extracted ; the red color is caused by a pigment termed capsicin, 
which can be separated from the pepper; and it might easily be sup- 
posed 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 p. 127; but Dr. Sauermann shows that it is not so. 
Yellow colored canaries were not in the very slightest degree affected 
by the pigment alone; but, curiously enough, parti-colored birds did 
react—the brown parts of the feathers became distinetly lighter in hue. 
It is a fatty substance (triolein) which appears to convey the pigment 
and produce thus a changing of the color from yellow to red; and 
further experiments were made with other birds, showing that it is not 
only canaries which are influenced by their food in this way. Some 
white fowls, belonging to a special breed, showed traces of yellow 
among the feathers after feeding with cayenne; but in this case these 
were not racial, but individual differences in susceptibility, for all the 
specimens of birds experimented with did not react to the stimulus. 
“ A similar series of experiments was made with some other colors; 
it was found with carmine that the yellow color was destroyed and the 
birds became white. This unexpected effect is explained by the fact 
that a mixture of violet and yellow produces white. The fact that the 
fatty constituent, triolein, plays the chief part in the coloring of the 
feathers may perhaps help to explain the very singular fact that the 
Amazon parrots change from green to yellow when fed upon the fat of 
certain fishes. 
“With regard to the white fowls referred to, the experiments made 
by Dr. Sauermann were particularly interesting. The interest lies in 
the fact that the pigment was not absorbed equally by all the feathers ; 
only special tracts were affected; the breast feathers, for instance, 
became red, while the head remained white. It is therefore quite cred- 
ible that in a state of nature partial alteration of color may be pro- 
duced by a change of diet.” 
*Archiv. Anatomie und Physiol., 1889. Physiol., Abtheil., 543. 
