OF BIRDS. 
161 
the membrane to draw over the eye; and the feathers 
and wings. Parts wanting in birds, are, teeth and lips; 
the bladder which they do not need; as they drink no 
more than just to moisten their food. Variations in the 
parts of birds, from those of men and beasts, are: in the 
ear, which is of a very peculiar make; in the division of 
the aorta in the spinal marrow, which is divided into two 
in the middle of the back; in the bones, which are all 
hollow; in the heart, which has a fleshy valve at the 
mouth of the vena cava; in the lungs, which are strongly 
joined to the back, for the greater conveniency of flight; 
in the stomach— birds have two or more, to supply the 
want of chewing; in the legs and feet; in their tails; in 
their pectoral muscles, which are the strongest of all, 
whereas in men the crural muscles are the strongest; in 
the brain, the cortical part being innermost, whereas in 
men it is outermost; in the bronchia, which extends to 
the very bottom of the abdomen, so as to contain a great 
quantity of air; in the ovaries, which in birds are single,, 
and fastened on their back. 
The following brief observations on the flight, and 
nidification of birds may be deemed interesting. 
The flight of birds is various. Kites, and most of the 
falcon tribe, glide smoothly through the air, with scarce 
any apparent motion of the wings. Most of the order 
of pies fly quick, with a frequent repetition of the mo- 
tion of the wings. Woodpeckers flv awkwardly, and by 
jerks, alternately rising and sinking. The gallinaceous 
tribes in general fly very strong, and swiftly; but their 
course is seldom long, by reason of the weight of their 
bodies. The columbine race is of singular swiftness;, 
witness the flight of the carrier pigeon. The struthious 
race cannot fly, but still in running, their short wings are 
of great use, like sails to collect the wind, and accelerate 
their motion. Many of the greater cloven-footed water 
fowls, or waders, have a slow and flagging flight, but 
most of the lesser fly swiftly, and most of them with ex- 
tended legs, to. compensate for the shortness of their 
tails. Rails and gallinules fly with their legs hanging 
down. Coots and grebes are with difficulty forced from 
P 2 
