402 
MR. YOUATT’s VETERINARY LECTURES. 
not so much resistance wanted, but greater freedom of action. 
The ox breathes partly through the mouth. 
In the dog, who breathes almost entirely through the mouth, the 
velum palati is still smaller, the tensor weak, and the circumjlexus 
powerful. When coryza runs on to catarrh, and the membrane 
of the pharynx sympathizes with, or rather partakes of the in¬ 
flammation, the velum palati becomes inflamed and thickened: 
it will not then act as a perfect veil or curtain; it will not adapt 
itself to every part of the opening, and there is a communication 
between the passages of the mouth and nose; and thus we fre¬ 
quently have the defluxion from the nose, tinged by the colour of 
the food, or particles of food mingling with it. We do not like 
to see this, because it proves to us the extent and the violence of 
the inflammation. 
Pharynx .—The pharynx, at which we are now arrived, is a 
membranous, muscular, funnel-shaped bag, extending from the 
root of the tongue to the larynx and oesophagus ; wider anteriorly 
at the back of the velum palati, and narrowing backwards until 
it terminates in the oesophagus. It is a powerful agent, by means 
of the muscles with which it is lined, in conveying the food from 
the mouth to the upper part of the gullet. This being its office, 
it belongs to the digestive system, and will be considered when 
we treat of that system. There is a bone, however, which con¬ 
stitutes a portion of its wall on either side, and common to 
it, to the tongue, and to the larynx, which must be now con¬ 
sidered. 
THE OS HYOIDES. 
The Os Hyoides of the Horse. —The os hyoides is so named 
from its resemblance, in the human being, to the Greek letter 
Upsilon. In our patients the similarity can scarcely be traced. 
In the horse it has much more likeness to a spur, and the semi¬ 
circular body and the neck of the spur are perfect. In the young 
animal this bone is divided into seven portions; in the adult 
animal it is clearly divisible into five. The body embraces, but 
not closely, the thyroid cartilage of the larynx, for you see that there 
is a cartilaginous, ligamentous substance intervening. This bone 
gives protection and support to the thyroid cartilage, and also at¬ 
tachments to several important muscles, as the hyo-glossus longus ,, 
to draw the tongue within the mouth, and the brevis having nearly 
the same office ; and the hyo-pharyngeus , to dilate the pharynx, 
and the anterior constrictor pharyngeus, to contract the pharynx, 
and some other muscles. The principal muscles of the body of 
the os hyoides, are the hyo-thyroideus , from the inferior border 
