The Larynx
is placed at the top of the windpipe, the exit from the lungs, and is also connected with the Schneiderian membrane. At its upper part is the
epiglottis
, the main guard against the passage of the food into the respiratory tubes, and, at the same time, of the instrument of the voice. It consists of five cartilages united together by a ligamentous substance, and, by distinct and perfect articulations, adapting itself to every change of the respiratory process and the production of the voice.
At the base is the
cricoid cartilage
, the support and bond of union of the rest. Above are the
arytenoid cartilages
, resting on the
chorda vocales
and influencing their action. The
epiglottis
is placed at the extremity of the opening into the windpipe, with its back opposed to the pharynx, so that when a pellet of food passes from the pharynx in its way to the œsophagus, the epiglottis is applied over the glottis, and by this means closes the aperture of the larynx, and prevents any portion of the food from passing into it. The food having passed over the epiglottis, that cartilage, from its elastic power, again rises and resumes its former situation.
thyroid cartilage
envelopes and protects all the rest, and particularly the lining membrane of the larynx, which vibrates from the impulse of the air that passes. The vibrations spread in every direction until they reach the delicate membrane of the tympanum of the ear. That membrane responds to the motion without, and the vibration is carried on to the pulp of the auditory nerve, deep in the recesses of the ear. The loudness of the tone — its acuteness or graveness — depends on the force of the expired air and the shortening or lengthening of the chord. Hence it is, that the tone of the bark of the dog, or the neighing of the horse, depends so much on the age or size of the animal. Thus we compare the shrill bark of the puppy with the hoarse one of the adult dog; the high-toned but sweet music of the beagle with the fuller and lower cry of the fox-hound, and the deep but melodious baying of the mastiff. I may, perhaps, be permitted to add to these, the whinnying of the colt and the neighing of the horse.
Each animal has his peculiar and intelligible language. He who has long lived among them will recognise the tone of delight at meeting, rising into and terminating in a sharper sound; the strong and elevated tone when they are calling to or challenging each other at a distance; the short expression of anger — the longer, deeper, hoarser tone of fear; the murmur almost as deep, but softer, of habitual attachment, and the elevated yet melodious token of sudden recognition. I could carry on a conversation with a dog that I once possessed for several minutes, and one perfectly intelligible to both.
of the larynx is a frequent and dangerous complaint. It usually commences with, and can scarcely be distinguished from, catarrh, except that it is attended by cough more violent and painful, and the dog expectorates considerably. Acute laryngitis is not so frequent an occurrence; but there is much danger attending it. Blood must be abstracted to as great an extent as the pulse will bear, or until it becomes evidently affected. To this must follow digitalis, nitre, tartar emetic, and aloes, and to these must be added a powerful blister. A considerable quantity is effused and organized, the membrane is thickened, perhaps permanently so, and the whole of the submucous cellular tissue becomes œdematous.
[a]The]
dog is subject to sudden attacks of
angina
. It has been imagined, from the appearances that are manifested, that some strange body is arrested in the windpipe or the throat. There is no dread of water or of the usual fluids; the dog will lap once or twice from that fluid which is placed before him, and turns slowly away from it; and this circumstance gives rise to what is called dumb madness. The dog barks in a particular manner, or rather howls like a rabid dog: he is out of spirits, has a strange, anxious, altered countenance, and is alternately cold and hot. Frequently added to this is redness of the buccal and nasal membranes. He refuses all solid food, and either will not drink or finds it difficult to swallow anything. His mouth is generally open, and contains a spumy matter exhaling an offensive smell. His tongue, charged with a great quantity of saliva, protrudes from his mouth, and the submaxillary glands are enlarged. To these appearances are added a yellow tint of the eyes, constipation, and a small quantity of urine, surcharged with a deep yellow colour. At this period the disease has generally reached a considerable degree of virulence. Often the inflammation extends to the back part of the mouth and larynx; and in this last case the respiration is attended by a hoarse, hissing kind of sound.
The progress of the disease is rapid, and, in a few days, it reaches its highest degree of intensity. It is always fatal when it is intense; and, when its influence is widely spread, it is a very dangerous complaint.
Somewhat rarely the subjects of it recover. After death we find great redness and injection in all the affected nervous surfaces, and indications of abscesses in which suppuration was not fully established.
[Contents]/[Detailed Contents, p. 6]/[Index]