V 
r 
THE 
J, 
VETERINARIAN. 
VOL. V. 
SEPTEMBER, 1832. 
No. 57. 
MR. YOUATT’S VETERINARY LECTURES, 
DELIVERED AT THE UNIVERSITY OF LONDON. 
> 
LECTURE XIX. 
The Thyroid Glands and the Trachea. 
WE have completed our survey of that important and com¬ 
plicated machine, the larynx. Before we inquire into the struc¬ 
ture of the simpler continuation of the respiratory tube, the 
trachea or windpipe, there is a small, firm, ovoid body, of a 
colour varying from dark-red to black, placed on each side of it, 
and immediately below the larynx, which attracts our attention. 
These are 
The Thyroid Glands. 
Their Structure .—Glandular they evidently are. In propor¬ 
tion to their size, they are abundantly supplied with blood. A 
considerable artery is given oft' from the carotid, immediately 
below its three terminating divisions. The veins may be clearly 
traced into the jugular, and are likewise of considerable com¬ 
parative bulk; and the nerves are derived from the guttural fila¬ 
ments of the par vagum. The thyroid glands adhere to the 
trachea by dense cellular substance, and they are connected with 
each other, not as has been generally described by an isthmus 
passing over the front of the windpipe, but by a kind of appen¬ 
dix, through which, however, no intercommunication of vessels 
can be traced. In the colt and the puppy they are considerably 
developed, and of a red colour, somewhat dark ; they diminish 
with the a^e of the animal, and in old horses become of a 
brownish or even blackish grey. When we submit them to mi¬ 
nute dissection, we find that they are enveloped by very abundant 
cellular tissue, under which is their peculiar investing mem¬ 
brane, smooth and glistening. We cut into them, and, as you 
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