Fig-. II, gives a lateral view of time contents of the chest, belly, and pelvis, supposing a scrtical section to be made through the spine, and the ribs, integuments, muscles, pleura, and peritoneum on the left side re moved. A, 13, C, the heart invested in its pericardium ; A, the left or systemic ventricle ; 13, time left, or systemic auricle ; C, the root of the pulmonary artery ; I), the arch of the aorta, rising above the pericardium ; E. time mini }ow) :•1111l; right carotid and right sub•rlavian : 1,e left carotid art.•ry ; (1, 1-1, the l•ll sub ry and cut and tied ; 1. the place where of the ptilnw at• or hyn.t_ ink veins enters the sys /emir atiri( ; K, thc left lobe of the lungs dray. n aside towards the spipe, so that the next the pericar dium, tvlueli IS 117th/rally cnncau, appears MI.VCN ; L. be cut cch,;c of the diaplcr.c in ; the Icit lobe of the liter ; N, (), the stomach a little. oistenducl With hind ; P, the spleen, rather of an unusual figure in this subject ; Q, 1., S, '1', the great ()melanin col my the bow els, and extending it littl: below the navel, being- in this subject unusually devoid of fat ; Q, R, q, r, t, the several ings of the colon or great intestine on the left side of die body ; Q, 11, q, the transverse arch of the colon ; y, thc splenie flexure ; 11, r, the left lumbar portion ; the left iliac portion ; x, I, the signioid flexure ; X, the rectuni; Y, V, V. one of the three bands of longitudinal muscular fibres Ihat extends along the colon from the ca rum to the re. clout ; S, 1', cc, u, the eonvoltitiow, uh the small intestines partly covered by the omentum ; 6, the urinary biaddt r, a little distc:nded with fluid, lying be tween the vermin and the pubis ; r, the prostate gland on the left side ; d, the left ve.sic :du ; e, the left ter separated a little from the bladder, to which it was here clo-,ely connected.
repesents a poi tion of that division of the small intestines r allcdjpjunum, taken from a person Ivho had died soon after eating, when the lacteals were dis tended with chyle. A, B. C, the outer surface of the intestine covered w ith coat, through which are seen the minute ramifications of the blood-vessels, end the commencement of the lacteals, which latter arc distinguished h• their white colour; 1), D, a portion of the mesentery, by which the intestine was connected with the rest of the canal ; E. F, G, the trunk and princi pal ramifications of the mesenteric artery ; H. 1, K, the trunk and principal branches or the mesenteric vein, closely accompanying those of the artery ; L, L, L, three of the mesenteric glands, with numerous lacteals entering them from the mesentery, and a few going out on the op posite side.
Onc..tNs In pursuing our description of the organs of the hu man body, the most natural order would be to follow the course of the aliment from the intestines to the cir culating system, through the lacteals and thoracic duct. To do this with advantage, however, it would be neces sary that our readers should possess some previous Lnowledge of at least that part of the circulating system into which the common canal of the nutritious fluid en ters, and along which it takes its course. This conside ration obliges us to deviate a little from the course of nature, and to describe the organs of circulation before we consider those of absorption.
The organs circulation consist of the heart, as the minim centre from which the circulating fluids are conveyed to every part of the body, and to which they are returned, to undergo a renovation of their properties, and be again distributed ; of arteries, for distributing the blood, and furnishing the various secretions ; and of veins, for bringing back that part of the fluids which has been exhausted of its i ital powers, by passing through the seieral secreting organs. The circula ting s) ,teen is naturally di i,ied into two s( is of or gans ; one destined lin• the distribution of the blood to all part., of the body ; the other to circulate it turough particular organs, by it is to regain what it had lust in this gene; al distribution. Boot these sets of organs are united in one common centre, the heart, \t Mich is, in f.Ict, a double organ, consisting of several distinct catitics, filled blood of a dillerent nature al.(1 appear-an c.
Of the Heart.
The heart lies in the inferior part of the cavity of the clues, a little towards the left side, but chiefly in the middle region of the chest, formed by that doubling of the general investing membrane of this cavity, which is called In, diastinum. The human heart, in its figure,
so nearly resembles that of the domestic quadrupeds which are employed as food, that we need not describe its general Form. In its natural position it lies upon its side, resting on the diaphragm, with its point a little for wards, and towards the left side, nearly opposite the space between the sixth and seventh ribs, against which it beats at each contraction. Its base lies a little backward or dorsad, toward, the right, and rather more atlantad than its point, owing to the greater convexity of the diaphragm at this part. The whole heart, and the roots of the large blood-vessel., that arise from it, and terminate in it, are surrounded with a strong firm mem brane, to be presently described, called tericardium, by which they are firmly connected to the diaphragm and the neighbouring parts. See Plate XIX. Fig. II. A, B, C.
We have said that the heart is a double organ. It is divided nearly in the middle by a strong partition called the srpruin of the heart, and composed of fleshy and tendinous fibres. On each side of this partition lie two considerable cat ities, with strong fleshy sides or wails. These cavities are called the ventricles of the heart, and have been distinguished by different names, according to their situation or uses. That which in the ordinary position of the human body lies towards the sternum, and a little towards the right side, has been called the right or anterior ventricle ; and that which looks tow ards the spine, and a little to the left, the left or posterior ventricle. We shall here follow Dr Bar clay's nomenclature, calling the former the nub/tonic ventricle, as it conveys the blood entirely to the lungs, and the latter the systemic ventricle, as this is the cen tre of distribution to the system at large. Attached to each of these ventricles at the base of the heart, and easily distinguished from them by their external projec tion, are two other cavities, also of considerable size, but not furnished with such strong fleshy sides. These cavities arc called auricles, as they project from the sides of the base of the heart like the ears of a clog from his head. That auricle which is most attached to the right or pulmonic ventricle has been called the right auricle, and that which is attached to the left or systemic ven tricle, the left auricle. We call the former the pulmo nic, and the latter the systemic auricle, as the one re ceives the blood that is about to be sent to the lungs by the pulmonic ventricle, and the other receives that which is to be distributed to the system by the systemic ven tricle. From each of the two ventricles arises a large tube with strong- muscular sides, called an artery. That which arises from the pulmonic ventricle is generally termed the pulmonary artery, as it i, the tube through which the blood is comeved to the lungs. In Dr Bar clay's nomenclature it is the pulmonic artery. That tube w Melt arises from the systemic ventricle is called aorta, and by Dr Barclay the sysk milt. iu tI t y , being the medium of distribution of the blood to tin system. In each at the atirlelk s terminate several large tubes, which are the trunks of the great veins. The auri cle receives two, One coining Front the atlantal parts of the body, thence call d the superior or descending vena cava ; the (Alm r coming from the sacral parts of the body, and calied the ihferior or ascending versa CaVa. These are by Dr termed pulmonic veins. Into the systemic auricle open four tubes bringing the blood from the lungs, tiller it has been distributed through those organs. These are commonly called the pulmo nary veins, and by Dr Barclay the systemic veins. The part of each auricle where tho venous tubes enter is more expanded than the rest of the auricle, and is called .sinus. That formed by the Cava•, has been termed the right sinus oldie heart, and we shall call it the pul monic sinus; while that formed by the meeting of the pulmonary or systemic veins, is the left or systemic si nus. having thus given a general description or the heart, and explained the several names by which its parts arc distinguished, we shall resume the subject, and consider each part a little more at large.