COMPARATIVE ANATOMY. 
as those of the teeth are in the marmnalia. 
Hence an enumeration of its different 
figures and consistence belongs properly to 
the department of natural history, where it 
forms the foundation of classific distinctions. 
The accipitres, or rapacious birds, have 
it very hard, hooked at the end, and fur- 
nished with a process on either side ; cal- 
culated, therefore, in all respects, for seizing 
and lacerating their prey. Those of the 
parrot kind have it also hard, for bruising 
the firmer vegetable fruits ; and tlie wood- 
pecker, nuthatch. See. for penetrating the 
bark of trees. 
Those birds, which take a softer kind of 
food, and which require a sense of feeling 
in the part, for distinguishing their food in 
mud, w'ater, &c. have it approaching to tlie 
softness of skin. Such are the duck, snipe, 
woodcock, &c. 
In several classes, particularly the acci- 
pitres and gallinae, the base of the bill is co- 
vered witli a soft skin, called the cire, of un- 
known use. 
The cervical vertebrae of birds are very 
numerous, and have a very free motion on 
each other. This great mobility of the 
neck enables the animal to touch every 
point of its body with the bill ; and thus 
supplies the want of tlie prehensile faculty 
of the anterior extremity. Tlie sternum is 
prolonged below into a vertical process 
(crista) for the attachment of the strong 
pectoral muscles which are the chief agents 
in the act of flying. In the male wild swan 
(anas cygnus) and in some species of the 
genus ardea, as the crane, this part forms a 
peculiar cavity for the reception of a con- 
siderable portion of the trachea. The 
crista is entirely wanting in the ostrich and 
cassowary ; where the sternum presents, on 
its anterior or under surface, an uniform 
convexity, and this peculiarity of structure 
is accounted for by observing that these 
birds have not the power of flying. 
The wings are connected to the trunk 
by means of three remarkable bones. The 
clavicles, which are always strong, consti- 
tute straight cylindrical bones articulated 
to the sides of the front of the sternum, 
and extending straight forw'ards. Their 
anterior extremities are connected to the 
sternum, by means of a bone peculiar to 
birds, viz. the fork-like bone, or, as it is 
more commonly termed, the merrythought. 
(Furcula, in French la lunette or fourchette.) 
The scapula, which is flattened in form, 
but elongated, extends backwards from the 
front of the clavicle, parallel to the spine. 
The point of the fork-like bone is joined to 
tlie most prominent part of the keel of the 
sternum ; and the extremities of its two 
branches are tied to the humeral ends of tlie 
clavicles, and the front of the scapula;, just 
where these bones join each other, and are 
articulated witli the humerus. Hence it 
serves to keep the wings apart in the rapid 
motions of flying. 
As a general observation, it may be 
stated that the fork is strong and elastic ; 
and its branches wide, arched, and carried 
forw'ards upon the body, in proportion as the 
bird possesses strength and rapidity of 
flight; and accordingly the struthious birds 
(ostrich and cassowary), which are incapable 
of this mode of progression, have the fork 
very imperfectly formed. The two branches, 
are very short, and never united in the 
African ostrich, but are anchylosed with the 
scapula and clavicle. The cassowary has 
merely two little processes, from the side of 
the clavicle, which are the rudiments of the 
branches of the fork. In tlie New Holland 
ostrich there are two very small thin bones, 
which are attached to the anterior edge of 
the dorsal end of the clavicles by ligament ; 
they are directed upwards towards the 
neck, where they are fastened to each other 
by means of a ligament, and have no con- 
nection whatever with the sternum. 
The bones of the wing may be com- 
pared on the whole to those of the upper ex- 
tremity in man : and consist of an os hume- 
ri ; two bones of the fore arm ; two of the 
carpus; two, which are generally consoli- 
dated together, of the metacarpus; one 
bone of the thumb, and two fingers. 
The stork, and some others of the grallee, 
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 eflFort- There 
arises from the fore-part of the head of the 
metatarsal bone a round eminence, which 
passes up between the projections of the 
pulley, on the anterior part of the end of 
the tibia. This eminence affords a sufS- 
cient degree of resistance to the flexion of 
the leg, to counteract tlie effect of the oscilla- 
tions of the body, and would prove an insur- 
mountable obstruction to the motion of the 
joint, if there were not a socket, witliin the 
upper part of the pulley of the tibia, to re- 
ceive it when the leg is in the bent position. 
The lower edge of the socket is prominent 
and sharp, and presents a sort of barrier to 
the admission of the eminence, that re- 
quires a voluntary muscular exertion of the 
