parrot's foot, 273 



not perch across, as most perching birds do, but length- 

 ways, or with the axis of its body parallel to that of 

 the branch, — it holds on by a combination of me- 

 chanical resistances, acting all in the same plane, 

 though in different directions ; and therefore anylateral 

 motion in the joints of the foot or leg would turn that 

 foot into an instrument of positive instability — a crow- 

 bar to wrench the bird from the tree. 



But when we consider the style in which the parrot 

 dimbs, we can easily perceive that the looseness and 

 twist, of the articulation of the toes especially, which 

 make it so bad a walker, are the very best for its pro- 

 per habit. It is the same with the twisted-limbed 

 mammalia, to which allusion has been made for illus- 

 tration ; they could not have performed their part in 

 the system of nature, unless they had had that very 

 formation which makes them appear so awkward 

 when out of their proper sphere. When we come to 

 notice the feet of the water-birds, we shall find 

 instances of structures differing from each other to the 

 same extent, and nearly in the same manner as these 

 differ ; and if it lay within our province, we could 

 easily show the very same differences of adaptation 

 and use, and the same perfect accordance of the one 

 with the other, in all animals endowed with locomo- 

 tion, whether vertebrated or invertebrated, and whe- 

 ther of the magnitude of whales or the minuteness of 

 animalculi. Throughout the whole there is the most 

 complete evidence of mechanical perfection, always 

 competent to effect its purpose without supplemental 

 aid. And among most of those cases, probably 

 indeed in every case of an articulated animal, whether 

 articulated internally in the skeleton, or externally in 

 the crust, where it has been supposed that suckers 

 and cements, and other clumsy contrivances have been 



