146 CLASS AVES. 



dead substance cannot co-exist with a living. The internal 

 force which should maintain it in its organised state is gone, 

 and destruction follows. 



Now moulting is nothing else but this natural death of some 

 part of each animated being, in consequence of the develope- 

 ment of other more interior parts ; and this peculiar function 

 is subject to certain laws which are tolerably constant. 



In the vegetable kingdom we observe, at the end of each 

 year, the fall of the leaves, flowers, &c., because these organs 

 have gone through all the natural phases of their existence. 

 The defoliation of trees, and the fall of their organs of repro- 

 duction, may be considered as their annual moulting, which 

 takes place also among other vegetable products, even among 

 evergreens, but in a manner less rapid and perceptible, as one 

 leaf successively replaces another. 



Could we doubt that the life of organised bodies corresponded 

 with the revolutions of the terrestrial globe, and that its phases 

 were regulated upon them, we should find a striking proof of 

 this truth in the defloration and defoliation of vegetables, and 

 the moulting of animals. In spring, all living and vegetating 

 nature renews and developes its productions ; the earth is 

 clothed with verdure, and the animal tribes become invested 

 in a fresh and more brilliant livery in this season of universal 

 reproduction. The cause of this grand external revolution in 

 all beings is this : during the winter their functions, long com- 

 pressed by the cold, have gained a superabundance of juices, 

 of sap, of nutriment, which only awaits the return of external 

 heat to assist its propulsion to the surface. Accordingly, at 

 the appointed season, the germs shoot forth with trebled vigour. 

 Everything in our organisation is equally propelled outwards. 

 A proof of this may be obsei'ved in the cutaneous eruptions 

 that so frequently appear on the return of spring. 



We find, then, the germs of leaves, of flowers, of fruits in 

 vegetables, the hairs, feathers, scales, horns, epidermis, &c., 

 in animals, increasing and developing themselves in spring, to 



