BIRDS IN GENERAL. 



4.31 



tory canal. It is true, indeed, that the horned 

 owl, and one or two more birds, seem to have 

 external ears; but what bears that resem- 

 blance are only leathers sticking out on each 

 side of the head, but no way necessary to 

 the sense of hearing. It is probable, how- 

 ever, that the feathers encompassing the ear- 

 holes in birds, supply the detect of the exte- 

 rior ear, and collect sounds to be transmitted 

 to the internal sensory. The extreme deli- 

 cacy of this organ is easily proved by the 

 readiness with which birds learn tunes, or 

 repeat words, and the great exactness of 

 their pronunciation. 



The sense of smelling seems not less vivid 

 in the generality of birds. Many of them 

 wind their prey at an immense distance, while 

 others are equally protected by this sense 

 against their insidious pursuers. In decoys, 

 where ducks are caught, the men who attend 

 tnem universally keep a piece of turf burn- 

 ing near their mouths, upon which they 

 breathe, lest the fowl should smell them, and 

 consequently fly away. The universality of 

 this practice puts the necessity of it beyond 

 a doubt, and proves the extreme delicacy of 

 the sense of smelling, at least in this species 

 of the feathered creation. 



Next to the parts for flight, let us view the 

 legs and feet ministering to motion. They 

 are both made light, for the easier transpor- 

 tation through the air. The toes in some are 

 webbed, to fit them for the waters; in others 

 they are separate, for the better holding ob- 

 jects, or clinging to trees for safety. Such 

 as have long legs have also long necks, as 

 otherwise they would be incapable of gather- 

 ing up their food either by land or water. 

 But it does not hold, however, that those ho 

 have long necks should have long legs, since 

 we see that swans and geese, whose necks 

 are extremely long, have very short legs, 

 and these chiefly employed in swimming. 



Thus every external part, hitherto noticed, 

 appears adapted to the life and situation of 

 the animal; nor are the inward parts, though 

 less immediately appropriated to flight, less 

 necessary to safety. The bones of every part 

 of the body are extremely light and thin ; and 

 all the muscles, except that immediately 

 moving the wings, extremely slight and fee- 

 ble. The tail, which is composed of quill 



NO. 39 Sf 40. 



feathers, serves to counterbalance the head 

 and neck ; it guides the animal's flight, like 

 a rudder, and greatly assists it either in its 

 ascent or when descending. 



If we go on to examine birds internally, we 

 shall find the same wonderful conformation 

 fitting them for a life in air, and increasing 

 the surface by diminishing the solidity. In 

 the first place their lungs, which are com- 

 monly called the sole, stick fast to the sides 

 of the ribs and back, and can be very little 

 dilated or contracted. But to make up for 

 this, which might impede their breathing, the 

 ends of the branches of the wind-pipe open 

 into them, while these have openings into 

 the cavity of the belly, and convey the air 

 drawn in by breathing into certain receptacles 

 like bladders, running along the length of the 

 whole body. Nor are these openings obscure, 

 or difficult to be discerned ; for a probe 

 thrust into the lungs of a fowl will easily find 

 a passage into the belly ; and air blown into 

 the wind-pipe will be seen to distend the 

 animal's body like a bladder. In quadrupeds 

 this passage is stopped by the midriff 1 ; but 

 in fowls the communication is obvious; and, 

 consequently, they have a much greater fa- 

 cility of taking a long and large inspiration. 

 It is sometimes also seen that the wind-pipe 

 makes many convolutions within the body of 

 a bird, and it is then called the labyrinth ; but 

 of what use these convolutions are, or why 

 the wind-pfpe should make so many turnings 

 within the body of some birds, is a difficulty 

 for, which no naturalist has been able to ac- 

 count. 



This difference of the wind-pipe often ob- 

 tains in animals that, to all appearance, are 

 of the same species. Thus in the tame swan, 

 the wind-pipe makes but a straight passage 

 into the lungs; while in the wild swan, which 

 to all external appearance seems the same 

 animal, the wind-pipe pierces through the 

 breast-bone, and there lias several turnings 

 before it comes out again, and goes to enter 

 the lungs. It is not to form the voice that 

 these turnings are found, since the fowls that 

 are without them are vocal ; and those, par- 

 ticularly the bird just now mentioned, that 

 have them, are silent. Whence, therefore, 

 some birds derive that loud and various mo- 

 dulation in their warblings, is not easily to 

 3X 



