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THE STOMACH OF THE HORSE
Is, as well as in all other animals, an organ of the first importance. In the horse it differs from most other grazing quadrupeds, as it consists of one pouch, or bag only, whereas in those that ruminate, or chew the cud, it is generally divided into four compartments.
In its shape it somewhat resembles a bag-pipe, but is larger on the left side than on the right. Its magnitude is, generally speaking, in proportion to the size of the horse ; although it is small when compared with that of other animals,
It is furnished with three coats, the outermost of which is the peritoneum; the second is muscular and fleshy; and the last a continuation of the innermost coat of the æsophagus, or gullet, which goes
from the mouth to the stomach and begins at the root of the tongue, behind the head of the windpipe. At that part where it enters the stomach, it is composed of a pretty thick substance, made up of circular and fleshy fibres, by which it contracts and dilates. This is called the left or upper orifice of the stomach, and that whereby it discharges itself into the duodenum is its right or lower orifice.
A great part of the stomach of the horse is insensible, in consequence of a cuticular covering, and differs of course from the villous portion of that viscus.
This insensibility prevents irritation from hard food. The æsophagus or gullet, is constantly, unless at the time of swallowing, drawn into longitudinal folds. This contraction prevents any return of the food, and also precludes the possibility of vomiting, from its acting as a valve against any substance that might be re
jected by the stomach. Vomiting indeed would produce suffocation in a horse, as owing to the peculiar structure of the superior portion of the pharynx, the food which was thrown up must necessarily drop into the trachea, or windpipe.
That part of the stomach which is not lined by cuticular membrane is extremely vascular. It occupies the posterior part, and is of the greatest importance to the animal economy.
The gastrica denter and sinister are continued in this membrane. Its surface is glandular, and it secretes the gastric juice. This juice is the principle agent in digestion, and acts alike upon all animal and vegetable substances that are taken into the stomach, and is so powerful as even to consume a part of the stomach itself after death. The mass which is produced by the action of the gastric juice generates a fluid, which is called chyle, and which is always the same in its quality, notwithstanding it may arise from a great variety of food.
The gastric juice coagulates milk, and it must undergo this process in the stomach before it can be digested; yet the gastric juice has no effect on animal substances that are alive, and this accounts for the circumstance of bots living in the stomach of the horse.
These insects attach themselves very firmly to the cuticle of the stomach, or the insensible part, by two hooks situated near the tail. In this situation they occasion little or no inconvenience to the animal. These insects appear to be insensible to pain, as even the most caustic and stimulating medicines will not dislodge them.
This may in part arise from their bodies being covered by a kind of hairy spiculæ which prevents any fluid entering into contact with the surface. Very few horses are free from bots at a certain part of the year, and it appears as if the stomach had been destined as the receptacle and support of those animals.
Mr. Bracey Clarke has lately published a very elaborate and satisfactory treatise on the different species of bots which infest not only horses, but cows, deer, and sheep.
According to his experiments, it appears that the fly depositing its eggs in the fundament of the hörse is both erroneous and absurd, and indeed it appears extraordinary how the insect could afterwards make its way into the stomach through the intestines, and that too in opposition to their peristaltic motion.
The reader will find both amusement and information in this valuable work of Mr. B. Clarke's.
The stomach of the horse is liable to inflammation, yet not so much so, perhaps, as that of the human being.
Inflammation of this organ is attended with extreme pain, the pulse is hard, the patient thirsty, he lies down and looks constantly towards the part affected. In this case large quantities of either solids or fluids ar: injurious.
Bleeding should be practised to a considerable quantity, and the external surface of the belly should be stimulated by rowels or blisters.
The surface of the body should be kept warmly clothed. Sheep and oxen are subject to a preternatural distension of the paunch, from taking in too large a quantity of food. If not soon relieved death ensues.
Fermentation takes place, and a considerable quantity of air is generated, which materially increases the disease.
With a view to giving relief, it is sometimes the practice to pierce with a knife, or some other sharp instrument, into the stomach, between the last rib and the hip-bone. As soon as the orifice is thus made, the inclosed air rushes out, and the muscular action of the stomach being restored, the animal is instantly relieved.
Sometimes, however, a part of the food is forced out along with the air, which, if it enters between the stomach and the cavity of the belly, acts as an extraneous body, and produces an irritation and inflammation which generally proves fatal.
Dr. Munro recommended the introduction of a flexible tube through the mouth into the stomach, but it has not been much adopted, as the country people generally prefer the summary method of piercing into the stomach.
The stomach in the human being is affected by sympathy from complaints in other parts, such as gout, &c.; but it is doubtful whether the horse is ever affected in the same way. This may, perhaps, arise from so small a portion of the stomach being vascular and endued with sensibility, and also from secreting a little gastric juice. It is not an easy matter to produce nausea in a horse. Hellebore an aconitum, to the quantity of half a drachm, it is said will bring on efforts to vomit.
Four ounces of emetic tartar have been given without exciting nausea.
Cerussa acetata, to the amount of half a pound, has been given without any perceptible effect, and the same experiment has been made with aquia lithary. acet. in a proportionate degree.
Jalap and bitter apple has been given in large doses without any obvious consequences.
Corrosive sublimate has been also administered from fourteen grains to three drachms and a half. From this last quantity inflammation arose in the stomach, and coagulable lymph was thrown out.
Calomel purges and irritates the superior part of the pharynx and the mouth, but do not seem to effect the salivary glands. There is, however, considerable danger in using it in large quantities.
Opium may be given in very large doses. Four ounces have been administered at a time.
Tobacco in every form has been employed, even an infusion of three pounds has been introduced into the stomach without effect.
Vitriolated zinc acts as a tonic when used in moderate quanties: the dose may gradually be increased to half an ounce.
The lacteals take up a fluid, called chyle, and convey it through the lympatic glands, where it seems to undergo some change, into the thoracic duct; from thence they proceed in the horse to the left jugular vein, but in the human to the left subslavian. This process renews the blood after its various losses. It has been doubted whether the absorbents take up the chyle by capillary attraction, or by some voluntary action of their own.
Having gone thus far into the animal economy of the stomach of the horse it will not be irrelevant to offer a few remarks on the general system and consequences of administering medicines in disease. That this is often done unnecessarily, and, of course, mischievously, has been very ably shown by Mr. Clark of Edinburgh.
“ If,” saye he, “a man or horse be in a state of bealth, what more is required, or how can they be rendered better? Health is the more proper state of