4*3 BIRDS. 



directed upward* and backward* attached to the middle pain of the 

 true ribs. 



The breast-bone (sternum), a part of the greatest consequence, being 

 the point of attachment for the most powerful of the muscles which 

 set the wings in action, is composed of five pieces strongly joined 

 together, and prolonged below into a crest (crisU) for that purpose. 

 The greater or less development of this crest or keel, and the greater 

 or less ossification of the component parts of the breast-bone, depend 

 upon the wants of the bird. Those birds whose flight is strongest and 

 most continuous have the crest very large, and the breast-bone pieces 

 very firmly cemented together, as any one may see who will examine 

 the breast-bone of a hawk, or eagle, or that of a humming-bird ; while 

 in the ostrich and cassowary this crest is entirely absent, and the 

 breast-bone presents a uniformly arched surface, somewhat like that 

 of a Highlander's target 



In the crane and in the male wild-swan there is a cavity in the 

 anterior part of the breast-bone for the reception of the involuted 

 wind-pipe (trachea). The connection of the wings with the trunk is 

 managed by means of the two clavicles, and of that peculiar fork-like 

 elastic bone commonly called the merry-thought (furcula). This 

 apparatus operates as an antagonist power to the action which would 

 bring the wings together in flight, did not these bones, especially the 

 merry-thought, keep the shoulders asunder. The greater or less 

 development of this bone depends* on the exigencies of each particular 

 cue. In birds whose flight is long and rapid it is strong, with the 

 branches widely arched and carried forwards on the body ; in birds 

 which do not fly at all, in the ostrich, cassowary, and emu, for instance, 

 the bone becomes a mere rudiment "In the ostrich," as Macartney 

 observes, " the two branches are very short, and never united, but 

 anchylosed with the scapula (shoulder-blade) and clavicle (collar-bone). 

 In the cassowary there are merely two little processes from the side 

 of the clavicle which are the rudiments of the branches of the fork. 

 In the emu there are two very small thin bones attached to the ante- 

 rior edge of the dorsal ends of the clavicles by ligaments ; they are 

 directed upwards towards the neck, where they are fastened to each 

 other by means of a ligament, and have no connection whatever with 

 the sternum." 



The wing-bones are the homologues or representatives of the arms 

 or upper extremities of man and of the monkeys. The following are 

 the bones composing the wing of a bird : The arm (os humeri) ; the 

 fore-arm, consisting of two bones (ulna and radius) ; the wrist (carpus), 

 formed by two bones ; the metacarpus, also made up of two bones ; a 

 thumb, or rather the rudiment of one, there being but a single bone ; 

 and two fingers, the finger next the thumb consisting of two portions, 

 and the other only of one. To this hand are attached the primaries, 

 or greater quill-feathers ; the secondaries are affixed to the fore arms ; 

 and the arm supports feathers of inferior strength and development, 

 called tertiaries and scapulars. The bone which represents the thumb 

 gives rise to the bastard quills, and along the base of the quills are 

 ranged the largest of those feathers which are denominated wini;- 

 coverts. Such is the structure of the ' sail-broad vans ' which waft the 

 condor over the Andes. 



Sonet of the Lower or Potterior Eflrcmitiet. These consist of a 

 thigh-bone i femur); leg-bones (tibia and fibula), for there are two, 

 though the fibula is very small, and becomes anchylosed to the tibia ; 

 one metatarsal bone (at the lower end of which there are as many 

 processes as there are toes, each process furnished with a pulley for 

 moving its corresponding toe) ; and the toes. Of these, three generally 

 are directed forwards and one backwards. This back toe, or great toe, 

 is wanting in some birds. In the swallows it is directed forwards ; in 

 the climbing birds the outer toe as well as the back toe are directed 

 backwards. The number of joints is generally progressive ; the bock 

 toe has 2, the next 3, the middle too 4, and the outer toe 5 joints. 



" The stork, and some others of the Gralla (Waders)," says 

 Macartney, "which sleep standing on one foot, possess a curious 

 mechanism for preserving the leg in a state of extension, without 

 any or at least with little muscular effort There arises from the 

 fore part of the head of the metatarsal lion, a round eminence, which 

 pass (Ml up between the projections of the pulley, on the anterior part 

 of the end of the tibia. This eminence affords a sufficient degree of 

 resistance to the flexion of the leg to counteract the effect of the 

 oscillation* of the body, and would prove an insurmountable 

 tion to the motion of the joint if there were not a socket within the 

 upper part of the pulley of the tibia to receive it when the leg i* in 

 the bent position. The lower edge of the socket is promin 

 sharp, and presents a sort of barrier to the admin-ion of the eminence 

 that requires a voluntary muscular exertion of the bird to overcome. 

 which being accomplished, it slips in with some force like the end of 

 a dislocated bone." 



Mutclei of Motion ami i ,i<r;iiimrnlt. 



" The muscles," writes Blumenboch, " in this class arc distinguished 

 by possessing a comparatively weak irritable power, which is .- 

 after death; and by their U-ndons becoming ossified as the animal 

 grows old, jwrticuhirly in the extremities, but sometimes also in the 

 trunk." 



The pectoral muscles, as w ,|x-ct fn-m the form of the 



sternum, exhibit, generally s|>eaking, the greatest development. They 



BIRDS. 4*1 



are three in number, taking their rise ehieHy from the ample breast- 

 bone, and all being brought to bear on the head of the arm (him 

 Of these, the first or great pectoral u *aid, as a general i 

 to weigh more than all the other muscles put together. Hi -MIL- from 

 the keel or crest of the breast-bone, the m. rr\ -tl>ui;ht, and last rib*, 

 it is inserted in that rough linear elevation which may be obaerved on 

 the bone of the arm of most birds. This bone it strongly 'Impresses, 

 and so produces the rapid and powerful motions of the wing, which, 

 acting on the surrounding air, carries the bird fonv:inl in its flight. 

 As an antagonist to the great pectoral muscle, the middle pectoral, 

 which lies under it, and whose office it is to elevate the wing, puts 

 forth its tendon over the point where the merry-thought is joined to 

 the clavicle and shoulder-blade. This point of junction acts as a 

 pulley for the tendon which is inserted in the upper pa.it of the bone 

 of the arm ; and by this contrivance the elevating power is situated 

 on the lower surface of the body. The third or small pectoral, aids 

 the great pectoral in depressing the wing. Thus some birds are 

 enabled to dart away with the rapidity of an arrow, while others soar 

 to a height invisible to the gaze of man. 



\Ve have already seen that the pelvis is prolonged backwards to a 

 considerable extent. This formation furnishes room for the attach- 

 ment of the muscles which set the posterior extremities in motion, 

 and enables them to perform the functions of walking, hopping, 

 swimming, climbing, and perching. To this end there are a set of 

 muscles which go from the pelvis to the toes. One of the flexor or 

 bending tendons given off from a muscle which comes from the bone 

 of the pubis runs in front of the knee, and all the flexors go behind 

 the heel, so that the mere weight of the bird will bend the toes. Any 

 one may satisfy himself that this operation is purely mechanical, and 

 not the result of muscular action, by making the experiment on a 

 dead bird ; when he will rind that the flexion of the knee and heel 

 will at once bend the toes. This admirable contrivance, useful as it 

 generally is, shows itself in the most striking manner when brought 

 to bear on the limbs of those birds which roost in trees. When all 

 the voluntary powers are suspended, such a bird enjoys the most 

 profound repose, and the most secure position on its perch, without 

 an effort 



Thi! integuments of birds are composed of the same parts as those 

 of the mum miter.-, with the addition of feathers, the peculiar co> 

 common to the whole class. The beak is covered with horn, ami at 

 its base, as in the birds of prey, there is a fleshy part called the 

 The lower extremities are protected above by a scaly skin, and the 

 bottom of the foot and toes by a callous modification of the same 

 integument Some, the turkey for instance, are furnished with hair 

 in certain situations. The feathers vary infinitely. When a bird has 

 just left the egg its covering is a downy kind of hair, several little 

 bundles taking their rise from one common bulb. This is the origin 

 of the future feather. A dark cylinder soon makes its appearance, 

 from the upper extremity of which the sprouting feather em* 

 while the lower extremity receives the blood-vessels which supply the 

 vascular nourishing pulp of the barrel. When this pulp has per- 

 formed its office, and the stalk and other parts of the feather are fully 

 developed, it shrivels up into the well-known substance which every 

 one finds in a quill when he cuts it for the purpose of making a pen. 

 The details of the development of the feathers are highly interesting, 

 and have been described at length by F. Cuvier in the ' Memoires du 

 Museum,' torn, xiii., and also in the artile ' Aves ' in the ' Cyclopaedia 

 of Anatomy and Physiology.' 



The care which nature takes for the development of that particular 

 part of the plumage first which the wants of the particular bird 

 demand is remarkable. A young partridge runs off as soon tut it is 

 hatched to pick up the pupa- of the ant, which the parent bird 

 scratches up for it Some time elapses before it is necessary that it 

 should fly; we accordingly find that the body from the moment of its 

 birth is protected with a close-set downy covering, while all the 

 strength is thrown into the thighs, legs, bill, and neck. The wings 

 are gradually developed afterwards. A young thrush or a youn_- 

 n.l is hatched nearly naked, and while its body presents only a 

 few scattered bunches of weak downy hair-like feathers, great progress 

 maybe observed in the formation of the quills and other wing-fe< 

 because from the habits of the bird it is necessary that it should be 

 able to fly as soon as it leaves the nest 



As a general rule the plumage of the cock bird far exceeds in bril- 

 liancy that of the lien ; and in all such cases the young at first put 

 on the more sum hre garb of the mother. When the cock and hen an 

 without much difference in this respect, the young have a jMirticular 

 i:/uishinK plumage of their own. 



moult or shed their feathers. The summer dress in many 

 specie* varies from that of the winter. 



The mode in which the plumage changes is well described in the 

 'Transactions of the Zoological Society' l.y Y anvil ; anil the same 

 able /oologixt has shown in the ' Philosophical Transactions,' and in 

 the Proceed inn* of the Zoological Society,' that the putting forth of 

 the plumage of the male bird is not confined to the female past the 

 age of reproduction (so many well known instances of which an 

 tiven by Dr. Butter. John Hunter, and others), but that the jjarb of 

 d by those hen birds which from malformation ..] 

 disease are rrndi -i vd unable to assist in the continuation of the .- ; 



