BIRD. 



395 



bones, not breaking by slight pressure (as a box 

 composed of one bone would be apt to do), but still 

 very firm and stiff, stiffer anteriorly in those birds 

 which fly much and powerfully, and more produced, 

 particularly both in the sternum and the ribs, in 

 birds which swim and dive. As a whole, it may be 

 said to admit of no lateral bending ; and the little 

 that it admits of in the vertical direction is confined 

 to the lumbar vertebra 1 . 



The bony part of the tail of birds is generally 

 short, the effective tail, as an organ of flight, being 

 composed of feathers , but in all birds which have 

 much motion of the tail, the number of vertebrae in 

 that organ is considerable, though each individually 

 is very short, and the whole tapers to a point. 



The wings, or anterior extremities of birds, which 

 correspond in position to the arms of man and the 

 fore legs in the mammalia, are adapted for flight only, 

 or, if they perform any other office, it is merely that 

 of balancing. Their general action in flight has 

 already been partially mentioned ; their several 

 purls, as they appear externally, will be mentioned 

 in the next section ; and their peculiar forms, as 

 adapted to the different habits of the various tribes 

 and genera, will be found in the accounts of these, 

 under their respective names. We shall here only 

 mention, therefore, that the bones of the moveable 

 part of the wing consist of a humerus, a fore-arm, 

 ami a hand ; the part answering to the fingers of the 

 latter being very much elongated, with only one 

 finger fully developed, but the rudiments of the other 

 more or less apparent, according to the power of action 

 in the wing. The flying feathers are placed upon these 

 bones, and the thumb generally carries a little 

 plume of stiff but short feathers, which is called the 

 bastard wing, and in some species it is armed with 

 a claw or spine. The head of the humerus is arti- 

 culated nearly where the scapular bones, which are 

 imbedded in the muscles on the shoulder, the cora- 

 coid bones which proceed from the anterior parts of 

 the sternum, and the furcal bone, or united clavicles, 

 which projects as an arch in front of the breast, 

 protecting the vessels of the throat, at the same time 

 that it keeps the heads of the coracoids and scapu- 

 lars in their proper places, meet each other. The 

 shoulder-joint, or articulation of the humerus, which 

 is the centre of the grand action of the wing, is 

 thus placed on the firmest of all supports a tripod, 

 which is the only number of supports that will form 

 a sure base upon all kinds of surfaces. In birds of 

 the most powerful wing, these three supports divide 

 the space round the articulation into nearly three 

 equal parts, and they do not differ much in strength ; 

 they all "give" a little, so that the joint is not 

 nearly so liable to dislocation as if the point to 

 which it is articulated were fixed ; neither is there 

 so much danger of fracture or of concussion to the 

 vital parts by any sudden jerk given violently to the 

 wing._ 



It is one of the most beautiful parts of the struc- 

 ture of animals, that those organs which have to per- 

 form the most violent motions are never directly arti- 

 culatcd on an immoveable base, or a base imme- 

 diately in contact with the spinal column, far less 

 with the bones of the head. There is always the 

 play of a slow-moving joint, or union of some 

 description or other, between the articulation of 

 tin: moveahlc bone and that bone which encloses 

 the nervous mass. By this means that mass is made 



to ride smoothly while the animal leaps, or bounds, 

 or flies, or otherwise acts powerfully and irregularly ; 

 just as the springs of a carriage enable those within 

 it to ride smoothly, notwithstanding the jolting of 

 the wheels upon an uneven road. 



The scapula, or blade-bone, has less motion in 

 birds than in mammalia, because, with the exception 

 of those mammalia which have flying membranes, 

 the motion of fore-legs is crosswise to that of wings. 

 In the bat tribe there is a slight approximation to 

 this species of insertion of the humerus in the large 

 clavicles and blade-bones ; though even in them the 

 adaptation for an organ of flight is much less perfect 

 than in birds. In bears, on the other hand, whose 

 habit is to climb trees and otherwise to hug by the 

 compression of the fore-legs together, the blade-bone 

 is very moveable, and there are no clavicles. 



Some of the birds which can fly, often use the half- 

 expanded wings to assist in balancing them when 

 they run ; and this habit is most frequent with those 

 that have the legs long. Some of the birds which 

 cannot fly, have rudimental wings, which they appear 

 to use for the same purposes. The only bird which 

 has the wings so perfectly rudimental and concealed 

 within the integuments as not to be of any use in 

 balancing, is the APTERYX (see that article) ; and it 

 has the legs very short and stout, and, though its 

 habits are not known, it is probably not much of a 

 runner. 



Those short-winged birds which dive under water, 

 whether they tread the water itself by means of 

 webbed feet, as is the case with the diving ducks, 

 and divers properly so called, or tread the bottoms 

 of the shallows with feet that have the toes free, as 

 is the case with the dipper, use the wings in the 

 water. But wings are not very efficient instruments 

 of progressive motion either on the ground or in the 

 water, though they are of advantage in balancing on 

 land, and in ascending or descending in the divers. 

 All wings, whether perfect or imperfect, are formed 

 and articulated on the same general plan ; and though 

 they admit of a little inclination to the front or the 

 rear, their principal motions are always across the 

 axis of the body. 



From what was formerly said of wings acting more 

 efficiently in an atmosphere rather rare than in a 

 denser one, it follows that they must act still less 

 efficiently in water than in the densest atmosphere. 

 Indeed water is so nearly of the same specific 

 gravity with the bird, that an action of the wings 

 analogous to that of flying in the air, could not 

 possibly be performed in the water. Air the free 

 air of neaven is therefore the proper element for 

 wings, and their proper function is flying ; so that 

 any other which they may perform must be regarded 

 as a departure from the typical character of a bird, 

 of which feathered wings are the grand external 

 characteristic. 



And here we may pause to remark on the wisdom 

 of an arrangement which ensures a species of tenantry 

 for the air, as beautiful as that of the most picturesque 

 inhabitants of the earth. Clothed in a plumage no 

 less durable than that of the most favoured of the 

 animal kingdom, and performing, in their aerial flights, 

 a series of gyrations ever varying both in form and 

 character, t6 say nothing of their changeful and 

 varied colours, which by the motion of the bird are 

 made to rival the glowing tints of " the arch of 

 heaven." 



