ARTERY, (normal anatomy): acrveta, airo TOO TOY ocega TvgEtv, ab aere servando. Tr. ar tery. Germ. Pulsader,Schlagader. Ital. arteria. The arteries are the vessels which carry the blood from the heart, and distribute that fluid throughout the body. The trachea was ori ginally called artery from the circumstance of its containing the air which it transmits to the lungs. The term artery was exclusively ap plied to the trachea by Hippocrates and his cotemporaries, by whom the vessels now called arteries were described as pulsating veins. Aristotle restricted the term artery to the tra chea, and described the aorta as the lesser vein. 'We find these vessels called arteries in the writings of Aretwus, Pliny, and Hero philus, probably on account of the adoption of the opinion of Erasistratus, who taught that they contained a vapour or spirit. The vessels now known as arteries, however, were more dis tinctly so designated by Galen, who affirmed that they were full of blood, and described the arteries and veins as forming each a tree, whose roots implanted in the lungs, and whose branches distributed through the body, were united by a common trunk in the heart.
There are two great arterial trunks—the aorta, which arises from the left ventricle of the heart, and the pulmonary artery, which arises from the right ventricle of that organ. Each of these vessels has an origin, a trunk, and branches, which divide and subdivide in an arborescent form, until they are reduced in size to the most delicate degree of minuteness, terminating in the capillary vessels, which can be traced entering into all structures except cartilage, hairs, and epidermoid parts. Striking as the contrast is between the size of the primi tive arterial trunks and that of the almost in visible capillary vessels, comparatively few divisions intervene between the two extremes of the arterial system, their number hardly exceeding twenty, as hailer ascertained by counting the divisions of the arteries of the mesentery between the place of their origins from the aorta, and their termination in the capillaries of the intestines.`'
That the arteries in general are circular tubes is evident from an inspection of their orifices when cut across, even in the dead body. The walls of the larger arteries, when empty, collapse, so as to present, on a trans verse section, an aperture more or less ellipti cal: when distended, however, either by the blood during life, or by injection in the dead body, these also are circular ; so that the circular form may be considered as universal in all parts of the animal system except at the origins of the aorta and pulmonary artery, where the circumference of each of these ves sels is distended into three sacculated pouches of equal size, called the lesser sinuses ; and in the ascending portion of the arch of the aorta, which has a dilatation on its right side, in creasing with years, called the greater sinus.
The arteries in general become smaller in their course in proportion to the number of branches arising from them. To this, however, there are exceptions, of which the aorta pre sents a remarkable example, being of as great a capacity near the origins of the primitive iliac arteries as it is in its thoracic portion, and the vertebral arteries are as large where they enter the foramen magnum of the occipital bone as where they arise from the trunks of the sub clavians, notwithstanding that they have given off many branches in the intermediate part of their course.
Wherever an artery runs for some distance without giving off branches, it appears to suffer no perceptible diminution in its size, as has been ascertained by the experiments referred to byBaron Haller,-1- and repeated by Mr.Hunter,::: in which the common carotids were found as capacious near the place of their division into the external and internal carotids as at their origins ; and the same remark being considered as equally applicable to all other arteries simi larly circumstanced, it has been stated in • general terms that the arteries and their branches are cylindrical, and that the whole of the arterial system is a series of cylindrical tubes.