A HISTORY OF 



swer to the fore-legs in quadrupeds, and at 

 the extremity of this they have a certain fin- 

 ger-like appendix, which is usually called the 

 bastard-wing. This instrument of flight is 

 furnished with quills, which differ from the 

 common feathers only in their size being lar- 

 ger, and also from their springing from the 

 deeper part of the skin, their shafts lying al- 

 most close to the bone. The beards of these 

 quills are broad on one side and more narrow 

 on the other, both which contribute to the pro- 

 gressive motion of the bird, and the closeness 

 of the wing. The manner in which most 

 birds avail themselves of these, is first thus : 

 they quit the earth with a bound, in order to 

 have room for flapping with the wing ; when 

 they have room for this, they strike the body 

 of air beneath the wing with a violent motion, 

 and with the whole under surface of the same ; 

 but then to avoid striking the air with equal 

 violence on the upper side as they rise, the 

 wing is instantly contracted ; so that the ani- 

 mal rises by the impulse, till it spreads the 

 wing for a second blow. For this reason, we 

 always see the birds choose to rise against the 

 wind, because they have thus a greater body 

 of air on the under than the upper side of the 

 wing. For this reason also large fowls do 

 not rise easily; both because they have not 

 sufficient room at first for the motion of their 

 wings, and because the body of air does not 

 lie so directly under the wing as they rise. 



In order to move the wings, all birds are 

 furnish I with two very strong pectoral mus- 



thing occurs in that of any of the other vertebrated ani- 

 mals. They stand more in need of the action of the air 

 than any other animals ; and their habits are such, that 

 they are less able to bear even the same action, by 

 means of the ordinary apparatus of lungs. 



The means by which the action of the air on the blood 

 of birds is rendered equal to the rapidity in circulation, 

 and consequent necessity of vital repair in that fluid, 

 without the painful fatigue of ever-panting lungs, is 

 made, like all other contrivances in nature, to answer 

 other important purposes at the same time. The lungs 

 of birds are ample in their dimensions, and have the cells 

 into which air is admitted larger than in the mammalia; 

 and they are kept in their places by being fastened to 

 the bones. Ramifications extend from them in tubes 

 and cells through the whole cavity of the body, into the 

 hollows of the bones, and, in short, along the course of 

 every artery which is not immediately embedded in 

 those muscles which are in action during the violent ex- 

 ertions of the bird. The blood-vessels in these muscles 

 are fewer than those in the muscles of the mammalia, as 

 any one may infer from the greater rigidity of their tex- 

 ture, and the whiteness of their colour. Thus, there is 

 not a blood-vessel of any considerable size in the whole 

 body of a bird, to the coats of which the air has not ac- 

 cess during the greater part of their course; and thus 

 the real action of breathing in birds is not concentrated 

 into one organ, to be toiling and panting there, as it 

 would be in the lungs of the mammalia, but distributed 

 over the whole circulation, and consequently diminished 

 in local intensity in proportion as it extended over a 

 greater surface. Mudiis Natural History of Birds. 



cles, which lie on each side of the breast-bone. 

 The pectoral muscles of quadrupeds, are trifl- 

 ing in comparison to those of birds. In quad- 

 rupeds, as well as in man, the muscles which 

 move the thighs and hinder parts of the body 

 are by far the strongest, while those of the 

 arms are feeble; but in birds, which make 

 use of their wings, the contrary obtains ; the 

 pectoral muscles, that move the wings or 

 arms, are of enormous strength, while those of 

 the thighs are weak and slender. By means 

 of these, a bird can mo^e its wings with a de- 

 gree of strength which, when compared to the 

 animal's size, is almost incredible. The flap 

 of a swan's wing would break a man's leg ; 

 and a similar blow from an eagle has been 

 known to lay a man dead in an instant. Such, 

 consequently, is the force of the wing, and 

 such its lightness, as to be inimitable by art. 

 No machines, that human skill can contrive, 

 are capable of giving such force to so light an 

 apparatus. The art of flying, therefore, that 

 has so often and so fruitlessly been sought 

 after, must, it is feared, for ever be unattain- 

 able ; since as man increases the force of his 

 flying machine, he must be obliged to in- 

 crease its weight also. 



In all birds, except nocturnal ones, the 

 head is smaller, and bears less proportion to 

 the body than in quadrupeds, that it may more 

 readily divide the air in flying, and make 

 way for the body, so as to render its passage 

 more easy. Their eyes also are more flat and 

 depressed than in quadrupeds ; a circle of 

 small plates of bone, placed scalewise, under 

 the outer coat of the organ, encompasses the 

 pupil on each, to strengthen and defend it 

 from injuries. Besides this, birds have a kind 

 of skin, called the nictitating membrane, with 

 which, like a vail, they can at pleasure cover 

 their eyes, though their eye-lids continue 

 open. This membrane takes its rise from the 

 greater or more obtuse corner of the eye, and 

 serves to wipe, cleanse, and probably to mois- 

 ten its surface. The eyes, though they out 

 wardly appear but small, yet, separately, each 

 almost equals the brain ; whereas in man the 

 brain is more than twenty times- larger than 

 the orbit of the eye. Nor is this organ in 

 birds less adapted for vision by a particular 

 expansion of the optic nerve, which renders 

 the impressions of external objects more vivid 

 and distinct. 



From this conformation of the eye it fol- 

 lows, that the sense of seeing in birds is infi- 

 nitely superior to that of other animals. In- 

 deed this piercing sight seems necessary to 

 the creature's support and safety. Were this 

 organ blunter, from the rapidity of the bird's 

 motion, it would be apt to strike against every 

 object in its way ; and it could scarcely find 

 subsistence, unless possessed of a power to 



