428 MR. youatt’s veterinary lectures. 
cartilage more resembles a bat crouching with its wings some¬ 
what expanded than anything else that I can liken it to. 
This interposition of ligament between the wings of the thy¬ 
roid cartilage is greater in the horse than in any other animal, 
except, perhaps, the bear and the seal. It can have no reference 
to the voice, but it is probably materially connected with the 
function of respiration. It is to enable this upper portion of 
the respiratory canal, partly filled, as we shall presently see, by 
the chordae vocales, to expand, when, in rapid progression, the 
animal requires a greater portion of arterialized blood, and atmo¬ 
spheric air must be admitted into the lungs in order to arterialize it. 
I have in a former lecture described the os hyoides as surrounding 
the anterior and upper edge of the thyroid cartilage, giving it 
support, and being the means by which motion is chiefly com¬ 
municated to the larynx as a connected body. You will observe 
the ligamentous substance (the ligamentum kyothyroideum), 
which is interposed between the cartilage and the bone, and you 
will remember the cartilaginous pillars (cornua), at the extre¬ 
mities of which the hyoid bone articulates with the cartilages. 
By means of these prolongations greater freedom of motion is 
given to the os hyoides, connected as it is with the tongue, than 
would consist with the function of the larynx. You will like¬ 
wise observe at the base of these cornua, and, a little anterior to 
it, two small apertures piercing the cartilage, through which pass 
the nerves that supply the muscles of the larynx. 
Following the posterior edge of the thyroid cartilage, we arrive 
at an angle, situated at its very base; and a kind of prolongation 
of it—the inferior cornua, by which it is articulated with the 
cricoid cartilage. We have here again a perfect joint, and the 
establishment of freedom of motion between the two cartilages. 
They are, besides this, connected together all round, both by 
muscular or cellular, or ligamentous substance. 
The Cartilages of the Larynx in the Ox .—We must now turn 
to our other patients. We shall observe manifest points of 
difference, and some of them we may trace to the difference of 
function required by the habits and destination of the different 
animals. In the ox the arytenoid cartilages approach nearer to 
each other; there is not the dilated opening into the wind-pipe.— 
Little speed is required in the labour of the ox. For the same 
reason, passing for a moment the epiglottis, the thyroid cartilage 
has not th e fissure which we have found in the horse. There is not 
occasion for the difference of expansion in this cartilaginous box, 
because there is not the occasional difference of speed. The 
thyroid cartilage is larger than it is in the horse, for what physio¬ 
logical reason I am unable to explain, except that the whole head 
