There can be no doubt that there belong to the circu lating system small vessels with open mouths, whether we call them c.zhaiing or seccrning vessels, by means of which the matters to be assimilated to the various parts of the body are conveyed to their destined situations ; iihosfihr.ric acid, and g•atIne to the bones ; fibrin( to the muscles ; albumen and gelatin( to the tendons and cartilages, &c. It is true that these are so small as to escape the investigation of the anatomist, but of their ex istence we can no more doubt than we can of that of the vessels to be presently noticed, by which these matters are again taken up, and carried back into the circula ting organs, to give place to fresh supplies.' The following table exhibits a comprehensive view of the origin, distribution, and connection of the princi pal arterial trunks and branches that have received par ticular names, and of the veins that accompany them, or correspond with them in name or situation. It is divi ded into four columns : In the first column are given the names of the principal arteries, according to the most received anatomical momenclator, and the synonymous names by which they are most generally distinguished. Where the principal trunk or branch gives off a number of smaller ramifications that have received appropriate :tames, the most important of these are enumerated in Italics, and a reference is given to such figures in our series of plates, as afford a representation of the vessel. In the second column are marked the origins of each artery, and in the third are given its general course and distribution. The fourth column contains the principal communications of the arteries with other arterial branches by inosculation, and their connection with the neighbouring veins and nerves.
In the above table we have marked the course and distribution of the principal arteries, so as to be best un derstood by the student of anatomy ; but it will be of con sequence to general readers to be informed where they may find sonic of the more important superficial arteries ; and we shall endeavour to convey this information in a style as familiar as possible.
The carotid arteries may be felt beating, by pressing with the fingers pretty strongly at the back of the wind pipe, about the middle oldie neck.
The firrial artery is very perceptible as it passes over the lower edge of the jaw-bone, about an inch from the posterior angle ; its branches, called the corollaries of the lips, may be felt on the inside of the lips. The buccal art cry may be felt in the fleshy part of the cheek, nearly opposite the second grinder of the lower jaw. The superficial temporal artery is extremely evident as it passes before the ear, and again as it rises behind the ridge of the temple.
The subclavian artery may be felt deep below the mid dle oldie collar-bone, between this and the first rib; the a rillary aro ry deep within the hollow of the arm-pit; the humeral is very perceptible as it passes down the inside of the arm close to the bone, on that side of the bicc/is muscle (which swells on bending the arm) that is next the little finger; and again, just at the bend of the elbow. The radial artery is that which
beats on the side of the fore-arm next the thumb; and sometimes the ulnar artery may be felt on the opposite side.
The femoral artery may be felt deep in the groin, about half way between the inner corner of the hip-bone .md the middle of the pubis or share-hone, in a hollow ')elow the ligaments and glauds, but can be traced little farther, as it is soon lost among the muscles. Scarcely any important arteries of the leg run so superficially as to be felt, except the arch formed by the anterior ti bial, which crosses over the middle of the back of the foot.
By attending to these hints, our general readers will be enabled either to guard against such accidents as may occasion these arteries to be cut or punctured; or when such accidents occur, will know where to apply the pressure of a pad and bandage, or of the fingers, to stop or moderate the effusion of blood. It must, indeed, be allowed, that in fat or muscular people, these arteries are often not very distinctly felt, but it is still useful to know the exact situations where they lie.
The heart, arteries, and veins, constitute the sangui ferous system, so called from their containing the blood, or general mass of circulating fluids. The nature and appearance of the blood demand our particular attention, as it is ultimately from this fluid that. all the parts of the body, whether solid or fluid, are derived. We shall, here, however, confine ourselves chiefly to its physical and more obvious properties, as the chemical considera tion of this fluid will form a prominent feature in our animal chemistry, while its motions within the contain ing vessels will be explained when we treat of the func tion of circulation, under PHYSIOLOGY.
Blood is a red fluid, of considerable consistency, a slight saline taste, a peculiar odour, and appears unc tuous when rubbed between the fingers. Its specific gravity is about 1.0527, or rather greater than that of Water.
While the blood circulates within its vessels, and when it is first drawn from them, it appears homogene ous; but on being suffered to remain at rest for some time, it separates into various portions, easily distinguish ed from each other. The greater part re:ttius its fluidity, is of a thin consistence, nearly transparent, and of a green ish colour. This is called the serum of the blood, from its resemblance to whey. Within this Iluid is seen a solid coagulurn or clot, of considerable firmness, and of a whitish or grayish colour on its upper surface, but tender, and of a deep red colour below. This is called the cruor or cra•samentum of the blood. The firm part on the upper surface, consists of what is called coagula ble lymph, while the lower part consists of the red glo bules which contain the colouring part of the blood. The cruor sometimes appears to float on the surface of the serum, but this happens only when there are numerous bubbles of air attached to its upper part ; for the specific gravity of this coagulum is greater than that of the se rum, or even of the blood itself before separation. The specific gravity of the serum is about Lo287, whereas that of the cruor is about 1.245.