ON THE TRACHEA OF BIRDS. 
401 
the oesophagus. The inferior larynx is singularly formed. At 
the termination of the trachea is a solid bony ring, with two con¬ 
necting bony processes, presenting a double aperture, each 
answering to the commencement of the bronchice in the quad¬ 
rupeds. Within these is found a duplicature of the membrane of 
the trachea, forming, as in the upper part of the trachea in our 
other patients, a fissure, or opening into the trachea, and being 
proper vibrating vocal ligaments. Tracing down the bronchial tube 
on each side, we find a thin membrane stretched across in the form 
of a drum, which is also connected with the voice, and the action 
of these membranes is governed by a system of muscles more or 
less complicated Here are several specimens, some of them, and 
particularly birds of song and imitative birds, have from three 
to five pairs of muscles belonging to this lower or bronchial 
larynx; and by means of them the two rimse glottidis, and the 
membranes of the bronchial tubes, are governed, as the rima glot¬ 
tidis in the quadruped ; while in the quadruped the power is 
wanting of lengthening or shortening the trachea. Some birds 
have only one muscle, as the owl, the cuckoo, and aquatic birds, 
that can utter only one monotonous sound. In others, the mus¬ 
cular apparatus is quite wanting, as in the greater part of water- 
birds, and some gallinacious birds, but not the domestic fowl. 
We have, then, the reed of the clarionet placed in the bronchial 
larynx, and played upon with more or less skill by a simple or a 
complicated system of muscles; while the tone is modulated by 
the superior aperture, and the loudness or roundness, the harsh¬ 
ness or the softness, of the voice is influenced by the convolutions 
and the complexity of the bony windpipe. But, gentlemen, I 
must break off: this w r ould be a most seducing subject; nor 
should I wander far from my proper ground, for not only the do¬ 
mestic quadruped, but the imprisoned warbler is my patient; but 
I leave this portion of the respiratory apparatus of the bird to the 
learned lecturer on comparative anatomy, who will do it far 
greater justice than I have time or power to do. 
OBSERVATIONS ON MR. JAMES TURNER’S 
THEORY OF ANIMAL HEAT. 
By Mr. Vines, V.S., Royal Veterinary College. 
On reading the number of The Veterinarian for June, 
l perceive that Mr. J. Turner, V.S.,of Regent Street, has intro¬ 
duced to our notice a new and ingenious theory respecting the 
production of animat heat during respiration, by means o( purely 
mechanical agency; namely, that the atmospheric air, in its ex- 
