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A Treatife on Farriery.

that turned towards the ftomach is unequally concave, and that turned towards the ribs, which is convex.

The principal artery of the fpleen proceeds from the cœlic, the vein empties itself into the vena portæ. The nerves

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very numerous, and form the Splenetic plexus. All thefe, when they enter into the spleen, are divided and fubdivided into a great number of ramifications, and accompany each other to the Jaft extremities of their divifions. They are contained in the common cellular capfule. The blood is extravafed among all these veffels, and kept in a web like cotton which is very fine, and spread throughout the whole extent of the spleen, and terminates in almoft imperceptible cells which communicate with each other.

The ufe of the Spleen is very hard to determine: however it is probable the blood is detained by this means a great while in the spleen, in order to prépare it for the feparation of the bile, which is afterwards to be performed, in the liver,

The capfula atrabiliares, called by fome the renal glands, are two glandulous bodies feated on each fide, a little obliquely on the upper and more internal part of the kidney, and are joined to it by a fine cellular web, and are covered by the external tegument of the kidney itself, called the adipous membrane. The fubftance of thefe renal glands is foft and fpungy, covered with a fine membrane, and their colour is yellowith. In a fœtus they are large as the kidneys. They have a cavity which contains a yellowif liquor, though by fome faid to be black. The use of thefe is hitherto unknown.

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The kidneys are two conglome

rate glands of a firm confiftence, and of a reddish brown colour. They are feated in the region of the loin, on the outfide of the peritoneum, and within its cellular web, one on the right end, and the other on the left, between the last of the falfe ribs and the bone called the ileum. The right lies upon the lower part of the liver, and the other under the spleen, which laft is commonly placed higher than the other. The right, kidney is fomewhat triangular, the left oval, and the higher part bigger than the lower.

The arteries belonging to the kidneys, are called the emulgent arteries, and are generally two, one for each kidney. The veins in the kidney accompany the arteries, and when they are united into one trunk, they are called the emulgent veins. A principal veffel belonging to the kidney is called the ureter. It is a membranous pipe which receives the urire, as it is feparated by the kidney, to carry it to the bladder.

The kidney has two coverings; the firft confifts of the cellular web of the peritoneum, and generally contains a great deal of fat. This being removed, you may difcover the proper tegument or covering of the kidney which it furrounds. It confifts of two lamine, which are united by a fine cellular web, and between these the lymphatic vel fels creep along.

The kidney is compofed of three different fubftances: the firft is the cortical, which confifts of a great number of blood and nervous veffels with glandulous grains. The fecond is tubulous, and is compofed of urinary pipes; which change into the third fubftance called the papillary, be

caufe

A Treatise on Farriery.

caufe it ends in ten or twelve papillæ full of finall holes, which open into the pelvis or bafon. This laft is the membranous ca. vity of the kidney, fending forth tubes or pipes which embrace the papillæ like funnels.

The ureters are membranous canals or pipes which reach from the kidneys to the bladder wherein they are inferted obliquely above its neck. The coats are fuppofed to be like thofe of the guts.

The bladder is a membranous bag, whofe fituation is well known, and is connected to the peritonæum only by its pofterior and fuperior part, and therefore may be opened without hurting that part. The force and lower part is called the neck. Its coats, like the inteftines, are common, mufcular, and nervous. laft being the inner, is exceeding fenfible.

This

Next the neck of the bladder

is the urethra, through which the urine is conveyed out of the body, and is much longer in horfes than in mares. The bladder is connected in horfes to the reguum or ftraight gut, and the feminal veffels; in mares to the vagina, and in both to the os pubis, by ligamentous and fleshy fibres.

In the middle of the upper part there is a ligamentous chord called the ruachus, which ter minates at the navel and is a continuation of the membranes. of the bladder. The kidneys feparate the excrementitious fluid from the blood, called the urine, which paffes through the papilla into the funnels, and from thence into the bafon, and is difcharged by the ureter into the bladder, where it remains for fome time by the help of a fphincter which furrounds its neck, and ftops its paffage, till an uneafinefs hap

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pens, which caufes à contraction of its mufcular coat; then with

the affiftance of the muscles of the belly and the midriff, the refiftance of the sphincter is overpowered, and fo the urine efcapes. The urine is much of the fame nature as the fweat, and they have fuch a relation to one another, that when the one is encreafed, the other is diminified.

The first thing to be confidered in the organs of generation, are the testicles or tones, whofe fituation is well known. Their shape is oval, a little flatted on the fides, their coverings are common and proper: the common is the fkin in which they are contained. which is divided into two parts, the one right and the other left, which outwardly appears like a feam. The proper membranes are, firft, the vaginal, which confift of feveral membranous cells, and is a continuation of the cellular web of the peritonæum and covers the whole testicle as well as its veffels. The fecond is a reddish membrane which adheres close to the former, and is only an expansion of a ligament. Under the vaginal coat there is a bag proper to each testicle, which furrounds them, and is only connected to the epididymes. Laftly, the albuginious which is strong, and adheres closely to the substance of the testicles. It receives the fpermatic veffels, and tranfmits them to the teftes. The proper vel. fels are the permatic arteries, which arife by a fmall beginning from the great artery, and the Spermatic veins.

The epididymes are two, one to each testicle, which lie on the fuperior part in the shape of a caterpillar. Their fubftance is vafculous, and all the veffels open

into

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A Treatise on Farriery.

into one duct called the vas deferens, by which it tranfmits the feed which it receives from the teftes.

The vas deferens is a whitish pipe which looks like a nerve, and reaches to the feminal veffels and the urethra. Their ufe is to convey the feed to the feminal veffels and to the urethra itself at the time of covering a mare.

of the body is the cheft, which is bounded on the lower part by the midriff, on the upper by the two first true ribs with the collar bones, on the fore part by the fternum and the extremities of the ribs, and on the back part by the extremities of the ribs that join to the back-bone, and by the back-bone itself.

The proper containing parts of the cheft are boney, flefly, and membranous. The boney parts

are the ribs, the vertebra of the back, and the fernum. The

The feminal vefels are feated under the bladder, near its neck, and are divided into varions cells, which communicate with each other. Each veffel has an excre-fleshy are the intercostal muscles, tory duct, which opens with a double orifice into the urethra on the under fide, near the neck of the bladder.

The yard is the chief organ of generation, whofe fhape and fize are well known. It begins with two bodies which unite under the os pubis, to which they are connected by a ligament. The inner texture is fpungy, on the under part of which is the urethra for the paffage of the urine before-mentioned. It is lined

with a membrane full of small glands, which feparate a liquor That defends it from the acrimony of the urine.

The parts of generation of a mare are analogous to thofe of a woman; and that they have a clitoris is plain from an hermaphrodite of this fpecies who was carried about for a fhow. The bottom of the womb is divided into two parts, called horns, as in other quadrupeds. But I need not be more particular in defcribing thefe parts, becaufe, if due care be taken, they feldom or never come under the confideration of a farrier.

the fernocostal, and the midriff. Among the membranous the pleura is chief.

The parts contained are the heart and the lungs.

The pleura is a membrane of a clofe texture, which lines the cheft throughout its whole extent, and fupplies the other parts contained therein with a covering. The internal furface of the pleura is fmooth and polished, and always moift with a ferofity that oozes from the pores, and is covered outwardly with a cellular web like the peritonæum, The pleura makes a fold or doubling at the vertebræ of the back, which terminates the whole length of the fternum The doubling is called the mediafiti

num.

It feparates the cheft into two parts, the one right, and the other left. It does not adhere to the middle of the fternum, but a little to the left, whence the right cavity is largeft.

The two lamine, whereof the mediaftinum confifts, are not fe parated from each other immediately behind the fternum in the fore part, but afterwards recede from each other to make room for feveral parts, as the pericardium, part of the windpipe, the THE fecond cavity of the trunk gullet, the thoracic dust, &c.

OF THE PARTS CONTAINED IN
THE THORAX OR CHEST.'

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Each

A Treatise on Farriery.

Each lamine forms a kind of purfe for each lobe of the lungs. The mediaftinum ferves to hin. der the paffage of any fluid fhed on one fide of the breaft from paffing into the other. This partition fecures a free breathing on one fide, if the cheft fhould be opened on the other. It also hinders one fide of the lungs from refting upon the other, when a horfe lies on one fide.

The thymus is a glandulous body feated in the upper part of the thorax, immediately under the fternum: its ufe is uncertain.

The pericardium is a membra. nous purfe of a close texture, which immediately inclofes the heart, and which is placed between the two leaves of the mediastinum; the figure is like that of the heart, but leaves room enough for its motions. It is connected to the mediaftinum, to the diaphragm, and to the great veffels of the heart. It contains a liquor to lubricate the furface of the heart, and ferves to keep it in its proper place.

The heart is a hollow mufcle of a conic figure, which is the principal organ of the circulation of the blood. The larger part is called the bafis, the fmaller the point. It inclines to the left, where its beating may be perceived. At the bafis of the heart are two fmall purfes which feem to be appendices, and are called the right and left auricles of the heart. The right is the largeft. They have each two orifices, whereof one anfwers to the vein which difcharges itself therein, and the other to its proper ven tricle. Each auricle confifts of a double row of femicircular fleshy fibres, and are ftrengthened by others, in the fhapes of columns between which there are con fiderable spaces. Thefe contract

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when the ventricles are dilated, and dilate when the ventricles are contracted; they being antagonift mufcles to each other.

The ventricles are two remark. able cavities; the one is the right, and the other the left. The right is thinner, weaker, and larger than the left. It receives the blood from the vena cava and the right auricles, and drives it into the pulmonary artery and the lungs. The left is ftronger and thicker. and not fo large. It receives the blood from the pulmonary vein and the left auricle, and forces it into the great artery.

The columna carne, or flefly columns, are in the ventricles as well as the auricles; and are fo many fmall mufcles, by the concourfe of whofe membranous fibres, are formed peculiar membranes, called valves, placed at the orifices of the auricles. The columns run tranfverfely from one fide of the ventricle to the other, partly that they may affift the contraction of the heart in the fytole, and partly to prevent too great a dilitation in the diastole

The valves are of three kinds :

tricufpidal, which are three, and placed at the orifice of the right ventricle, which fanfwers to the auricle on the fame fide. Mitral, which are feated in the left ventrical where it communicates with the auricle, preventing the returning of the blood into the heart from the veins. The femilunar, which are three, and are placed at the beginning of the great, .as alfo at the pulmonary artery, to hinder the return of the blood from the arteries into the heart.

The mufcular fibres of the heart are in fome places ftraight, in others fpiral. Thefe are of a

double

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A Treatise on Farriery.

double order; the external, which, run from the basis and tendon of the heart towards the left; the internal, which run towards the right, and interfect the former. When they act, they conftringe their cavities regularly, and expel the blood, which is called the fyftole. When they are relaxed, the two ventricles are dilated; this is called the diaftole. The auricles are, the two, hollow mufcles which are the antagonists of the ventricles, for they coutrac when the ventricles are dilated; and when the ventricles contract they are dilated, as was obferved before.

The blood-veels of the heart are of two kinds; the proper weins and arteries, called the coronary, diftributed through the heart; and the common, of which two are veins, the vena cava, and the pulmonary vein: and two ar. teries, the great artery, and the pulmonary artery.

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The use of the heart is to promote the circulation of the blood; for it receives the blood from all parts of the body by the veins, and by its contraction fends it back to all parts of the body by the arteries. Upon thefe not only the functions of the body depend, but even life itself.

The lungs, commonly called the lights, is the largeft vifcus in the cheft, and is divided into two parts or lobes, one on each fide of the mediaftinum, and contain the heart in the middle. They are not fubdivided in a horfe fo much as in other quadrupedes. Each lobe is divided into small cells, which are the extremities of the afperia arteria, whence the fubftance is veficulous and fpungy.

The lungs are not only connected to the fternum and to the vertebræ of the back by the me.

diaftinum, and to the heart by its veffels, but also to the pharynx and the tongue by means of the windpipe. There are alfo two membranous ligaments, which advancing from the pofterior edge of each lobe, terminate in the vertebræ of the back, as far as the diaphragm.

The lungs are covered with a membrane which is continued to the pleura. This membrane has two laminæ, the internal of which forms feveral partitions which penetrate into the fub. ftance of the lungs, and divide it; into innumerable fmall bodies called lobules, of various angular figures. These lobules have spaces between them, in which the nerves and blood veffels lie, which make ramifications on the external furface of the lobules. There is likewife a cellular web in thefe fpaces, which furrounds the nerves and blood veffels.

The air cannot pafs from one of the lobules into another, but only from the lobules into the cells which furround the bloodveffels which lie therein, and back from thefe fpaces or cells into the lobules. There are therefore two forts of cells, the bronchic cells, of which the lobules confift, and the vafcular cells, which furround rhe veffels.

The trachea arteria, or windpipe, begins at the bottom of the mouth, and runs along the middle and anterior part of the neck, and goes to be diftributed into the lungs by a great number of ramifications. The upper part of this is called the larynx, and the ramifications in the lungs the bronchia. The trachea arteria is a pipe which is partly cartalaginous, and partly membranous; the former is the fore part, and the latter is the hind part.

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