1888. | NEW YORK ACADEMY OF SCIENCES. 91 
lem. I fail to see, however, why the soaring of a toy kite does 
not furnish a key to the problem, a view of the matter now quite 
generally entertained. If we compare the soaring bird to a fly- 
ing kite, and let the weight of the bird be represented by the 
string which holds the kite at anchor, and let the expanded 
wings and tail represent the body of the kite, and add the sensi- 
tiveness and intelligence of the bird asa steering power, have we 
not all the elements of the problem? ‘The bird instantly per- 
ceives the necessity for any change of direction to maintain its 
position, and adjusts itself to the requirement by a slight move- 
ment of the tail or a slight inclination of the wings. I am per- 
fectly familiar with a large part of the abundant literature on 
the subject; but it is foreign to my purpose to discuss the matter 
in the present connection, as it has been very well presented in 
the paper read by Dr. Holder at the meeting of Dec. 19th. 
Passing now to the mechanism of a bird in its relation to 
flight, it may not be amiss to recall the fact that a bird is pre- 
eminently a flying vertebrate, and that every function and every 
organ, in short, the whole plan of organization, has reference to 
aérial life. The general form ofa bird is that of two cones placed 
base to base, the neck and head forming the apex of one and the 
tail the apex of the other. It is clothed with a covering of 
elastic feathers, which are imbricated backward, and conceal all 
angularities of the body, presenting at all points a smooth and 
rounded exterior. ‘The feathers are of the lightest texture, their 
shafts largely filled with air, as are likewise all the interstices be- 
tween the downy filaments. The bones are for the most part 
hollow, and air-sacs are distributed throughout the body. ‘lhe 
mode of reproduction is non-gestatory, and the bird is thus never 
impeded by the weight of its offspring. The principal muscles, 
those of flight, and the intestines, are on the lower side of the 
body, and so massed as to give alow centre of gravity. The 
bones that enter into the shoulder-girdle or scapular arch are 
all strongly bound together, giving firm support to the fore 
limbs, which are especially modified into organs of flight and 
adapted to no other purpose. ‘The wings are attached to the 
highest part of the body, leaving nearly its whole weight below 
the axis of support, this giving the greatest possible force to the 
wing-stroke. 
Of the bones, the sternum, with its great length, its broad 
lateral expansion, and its strongly developed keel, forms pri- 
marily the basis of the mechanism of flight, giving not only a 
large surface for the attachment of the immense muscles which 
move the wings, but one to which all the other bones concerned in 
flight are firmly bound. In front are the large coracoids, which 
run from the front edge of the sternum to the shoulder joint, 
into which they enter as important elements, besides affording 
