234 OBSERVATIONS ON THE CHANGES OF 



with certaiiit}^ of all other quadrupeds. The Horse, although it sheds 

 its coat freely in spring, is irregularly losing and restoring its hair 

 throughout the year. A change in food or in health is continually ac- 

 celerating or retarding this process. 



If some apology be requisite for these somewhat desultory remarks, 

 and for having entered so much into detail, it may be offered, in defence, 

 that the subject on which it treats, although apparently trifling and 

 unimportant, leads to many inquiries in philosophy and in natural sci- 

 ence. In investigating the changes from brown to white, in some 

 quadrupeds, we are led to inquire into the cause of this change. If it 

 be answered that it is the effect of cold, the question will naturally 

 arise, Why does not cold produce the same effect on other animals? 

 Why do not the Fox, the Raccoon and the Bear, residing in the same 

 neighbourhood, also become white in winter? Besides, the change 

 commences in the heat of summer. The Polar Hare, brought by Au- 

 dubon, was undergoing the change on the 15th of August. The Er- 

 mine was becoming white in the middle of October, in Carolina, when 

 the weather was still very warm. The emperor of China is said to 

 have preserved the Lepus variabilis in the warmer parts of his domin- 

 ions, and even there it was subject to become white. This colour, 

 then, rather anticipates than succeeds cold weather, and it would seem 

 as if there was some constitutional predisposition of the animal to the 

 change. A further examination into these mutations of colour to which 

 birds are subject, may extend our knowledge of physiology in regard 

 to the development and growth of feathers, and the process by which 

 their colours are imparted. Although it is generally admitted that 

 there is no circulation in hair or feathers, still this point does not appear 

 to be fully determined. Bichat* supposed that there was a species of 

 circulation in the interior substance of the hair, by which he endea- 

 voured to explain the changes of colour. This opinion, however, has 

 been contradicted by modern physiologists, who suppose the hairs to 

 be constituted by a colourless, transparent epidermic or horny sheath, 

 filled with a species of coloured pulp ,• and they contend that the hair 



* Anatomie Generale, Tom. II., p. 788. 



