36 



Conservators of museums very frequently notice that certain 

 birds in the collections bleach, particularly Avhen exposed to 

 light. A red-breasted Merganser {Mergus merganser) which 

 Dr. Weinland saw, when just shot, with a red breast, and which, 

 after having been deposited in the museum for some time, pre- 

 sented a pale whitish breast, showed this very remarkably. He 

 afterward obtained a bird of the same kind, and, when fresh, 

 examined its breast-feathers with a high power of the micro- 

 scope, and found all the pinnulte filled in spots with lacunes of a 

 reddish fluid, which, from the dark appearance of their margins, 

 seemed to be of an oily character. Some weeks afterwards the 

 same feathers, having been exposed to the light, had become 

 nearly white, and he found in the pinnulje, instead of the reddish 

 lacimes, only air-bubbles, which it is known produce a white color, 

 as in the case of the lily, which is rendered white by the air in 

 its cells. This observation led him to the conclusion, that in this 

 case the evaporation of the reddish fluid, and the filling of the 

 spaces with air, produce the change of color. If this fluid is an 

 oily matter, as there is reason to suppose, it will be readily 

 admitted, physiologically, that it may be furnished by the organ- 

 ism, by imbibition through the tissues, in consequence of a certain 

 disposition of the nerves leading to the skin and to the sac of 

 the feather in the skin, (even if the vessels and the nerve in the 

 feather itself should be dried,) for fat goes through all tissues 

 without resistance, and also through horn. Thus the fat coloring 

 matter may flow out into the feathers during the time of reproduc- 

 tion, which is the richest season in every living organism ; and 

 then again, from want of food, cold temperature, weakness, 

 decrepitude, or from strong emotions of the central nervous 

 system, from sudden terror or grief, — the same coloring fat may 

 be called back to furnish the suffering organism. 



This process, effected by different physiological conditions of 

 the organism, seems to be a reasonable explanation of the fact, 

 that many northern mammalia and birds become white in winter, 

 while they ai'e dark-colored in summer ; that the hair of men 

 or mamraaha, or the feathers of birds, may become suddenly 

 gray or white from sudden terror, hard labor, or debility, while 

 they are dark colored in mature life or in the more vigorous sea- 

 sons of the organism. And if we add the hypothesis, that in the 



