INTRODUCTION. 
21 
It is remarkable, that many fish- eating birds have an ex- 
tremely slender and elongated intestine, while others have 
it moderate in both respects, and in others it is both long 
and wide. Why these differences should exist, is not Very 
apparent ; but I have observed, that in all those piscivorous 
birds which plunge headlong or dart upon their prey, it is 
very slender. Even among the Falconinsc, the species 
which feed on fishes, as the Osprey and Sea-Eagle, have the 
intestine thus modified. 
The vocal and respiratory organs, being alluded to in the 
ordinal characters, may be now briefly noticed. In all birds, 
the trachea , or windpipe, is composed of a series of complete 
cartilaginous or bony rings, constituting a flexible tube, ca- 
pable of being shortened or elongated by the action of two 
lateral muscles, and the peculiar manner in which the rings 
are made alternately to overlap each other. The upper 
aperture of this tube forms a longitudinal slit, which is 
opened or closed by muscles acting upon the cartilages or 
bones which form its frame. It is in this upper or anterior 
part, the larynx, that the voice is produced in the mamma- 
lia ; but in birds, although the larynx and mouth may mo- 
dify the voice, its peculiar organ is the lower part of the 
trachea, where it divides into the two bronchi which go to 
the lungs. The last ring is divided by a bony partition, 
and furnished with membranes, the action of the expired air 
on which causes sound. The modulations of sound are pro- 
duced here by the action of small muscles upon the rings 
and membranes. Birds which emit merely a scream, or un- 
modulated sounds, have no peculiar muscle at this part ; such 
are Vultures, Swifts, Pheasants, Partridges, Pelicans. Those 
which emit sounds slightly varied have a single pair of mus- 
cles ; as Hawks, Woodpeckers, Pigeons, Pails, Gulls, and 
Divers. Some have two pairs, as Parrots ; the Kingfishers 
have three pairs ; and all the Cantatrices, Deglubitrices, and 
Vagatrices, have four pairs. The form of the inferior la- 
rynx varies much, being small or large, compressed, flat- 
