406 



BIRD. 



preyer, it must often prey in lowering and cloudy 

 weather, its power of vision must be strong in pro- 

 portion. It must also, adapted as its plumage is to 

 the violence of storms, have some very acute means 

 of general perception, otherwise it could not return 

 to the islands which it inhabits, after its long excur- 

 sions over the northern ocean. 



The most remarkable general property of this 

 skeleton is its compactness, and the equal perfection 

 with which, as an artist would say, all its points are 

 made out. None of the bones are very long ; and 

 those of the legs, as the bird is not much in the habit 

 of walking, are rather short ; but they are firm and 

 well proportioned, and the processes toward their 

 extremities, whether for giving firmness to the joint, 

 insertion to the muscles, or lever power to the ten- 

 dons, are very conspicuous. 



The general form of the spine, as it has already 

 been hinted at, can be seen in this example. The 

 vertebrae of the neck all admit of ready motion ; and 

 the position of repose, or that in which all the bones 

 bear equally upon each other, is a curve. 



All the vertebrae of the back, at least as far as the 

 posterior edge of the sternum on the other side, are 

 soldered together, and afford a firm base for the blade 

 bones, which are considerably produced, and lie 

 nearly parallel to the mesial line of the spine. The 

 eoracoid bones are strong, and enlarged at their 

 extremities where they meet the anterior edge of the 

 sternum, though they are more flattened there, so as 

 to agree in thickness with that bone. The furcal 

 bone is also a perfect, circle, and placed with its flat 

 side in the direction of the strain, so that it resists the 

 separating or bringing together of the shoulder joints, 

 the grand centres of motion for the wings, in the most 

 powerful manner that could be obtained from the 

 same quantity of bone. This bone, it will be per- 

 ceived too, forms a large opening, in which the neck 

 can play freely, without the least pressure upon any 

 of the important vessels which it contains. 



All the bones of the wings are well formed, and the 

 fingers, though only one of them is perfect, can be 

 distinctly traced. The humerus is the longest and 

 also the strongest and heaviest bone in the wing ; 

 and the lengths of the others diminish in the pro- 

 portion of their other dimensions ; so that though 

 when the wing is moved, the different parts move 

 with velocities proportional to their distances from 

 the centre of action, yet the effect of the entire wing 

 is very uniform, and the bird, when in powerful action, 

 may be said to fly with the whole of it, that is, to 

 strike the air with nearly equal effect with the whole 

 of its under surface. The stiffness of the intermediate 

 joints in such a wing, the perfect freedom of the 

 shoulder joints, and the remarkably steady base which 

 from their size, form, and place, the scapular, the 

 eoracoid, and the furcal bone, give to the centre of 

 action, render the flight of the bird exceedingly 

 smooth ; and, though it is heavy for its bulk and even 

 for the length of its wings, the jer falcon never 

 appears in the least to labour on the wing. Birds 

 more loosely boned, in any of the respects that 

 have been mentioned are incapable of this perfect 

 steadiness and beauty of flight. The short winged 

 ones of them flutter, as if they had not wing enough, 

 and the long winged ones have their bodies tossed 

 upward by the down stroke of the wings, and down- 

 ward by the up stroke, as if their wings wore too 

 much for their management. This falcon, how 



ever, which has- to range over somewhat bare and 

 very stormy pastures, has its wings and its body 

 adapted to each other with the utmost perfection, so 

 that it can rush onward in any line of direction that 

 it pleases, without the least deviation ; therefore it 

 flies from point to point by the shortest line possible ; 

 and thus while it is the perfect model of power in 

 flight, it is at the same time the perfect model of 

 economy. 



The lumbar portion of the jer falcon's spine admits 

 of a little bending downwards, so that the articula- 

 tions of the femoral bones, or those joints which 

 answer to the hi)) joints in the mammalia, can be low- 

 ered a little. The bones of the tail are also more 

 numerous and better " made out" than in most birds. 

 This arrangement of the p'osterior portion of the 

 sternum, enables the falcon to perform more effec- 

 tively its double action in the air, as by this bending, 

 the foot, with which it strikes its prey, can act so far 

 below the plane of the wings as not to interfere 

 with their motion of flight. Not only this, but it also 

 affords a support to the tarsus, upon the joint of 

 which the whole force of the stroke would otherwise 

 be thrown as a cross-strain ; and, though that joint 

 is a firm one, yet it is contrary to the general law of 

 nature's mechanics, to subject even the firmest joint 

 to the greatest strain which it has to bear in the least 

 favourable position. Indeed, there is seldom auy joint 

 subjected alone to a very great strain, in the natural 

 action of animals. As there is but one life in the 

 animal structure, so there is always concerted action 

 when that life is strongly cxeited, be the object of 

 the excitement or the organisation which it more 

 immediately sets at work, what they may. There is 

 some part upon which, in case of partial failure, the 

 acting part can fall back for support if not. for assist- 

 ance ; and the very fact that organs which have to 

 perform violent motion, are connected with several 

 centres, and those centres all susceptible of yielding 

 to some extent or other, shows that the animal is 

 organised for a concert of the parts in its action. 



There is much firmness in the foot and leg of the 

 falcon, and the position in which the foot is carried 

 when hawking, stiffens the hind toe by pulling the 

 tendon, and that without any muscular exertion, to 

 the very angle at which the claw gives the stroke 

 with the greatest effect. It is an oblique thrust, 

 neither directly against the end of the last phalanx 

 of the bone, nor across it, but in a tangent to the 

 curvature of the claw at its point ; and any one upon 

 examining the foot of a falcon, will find that this is the 

 very direction in which a shock can come so as to 

 jar or strain the least possible, and at the same time 

 to divide the pressure most equallv among all the 

 joints of the member which acts, if the stroke were 

 given directly in the line of the axis of the toe and 

 claw, the crush or jar would be the greatest possible ; 

 and any one who unwittingly strikes the point of 

 the stiffly extended finger against an obstacle can 

 tell how much more painful it is than if the yielding 

 finger struck the same obstacle with double the force. 

 There is another very appropriate illustration : by 

 holding the joints of the legs and feet easy, one 

 can drop upon the feet from a considerable height, 

 not only without risk, but with little pain or shock 

 at the moment ; whereas if one were to drop 

 even two or three feet with all the joints of the leg* 

 and feet kept purposely extended and rigid, the 

 pain from the jarring would be" considerable, aud 



