. Anatomy, descriptive and applied. Anatomy. 580 THE VASCULAR SYSTEMS Between the origin of the left subclavian artery and the attachment of the liga- mentum arteriosum the kimen of the fetal aorta is considerably narrowed, forming what is termed the aortic isthmus {isthmus aortae), while immediately beyond the liga- mentum arteriosus the vessel presents a fusiform dilatation which His has named the aortic spindle (aorfenspinder)—the point of junction of the two parts being mai'ked in the concavity of the arch by an indentation or angle. These conditions persist, to some extent, in the adult,
. Anatomy, descriptive and applied. Anatomy. 580 THE VASCULAR SYSTEMS Between the origin of the left subclavian artery and the attachment of the liga- mentum arteriosum the kimen of the fetal aorta is considerably narrowed, forming what is termed the aortic isthmus {isthmus aortae), while immediately beyond the liga- mentum arteriosus the vessel presents a fusiform dilatation which His has named the aortic spindle (aorfenspinder)—the point of junction of the two parts being mai'ked in the concavity of the arch by an indentation or angle. These conditions persist, to some extent, in the adult, where His found that the average diameter of the spindle exceeded that of the isthmus by 3 mm. (about one-eighth of an inch). Peculiarities.—The height to which the aorta rises in the thorax is usually about an inch below the upper border of the sternum; but it may ascend nearly to the top of that bone. Occa- sionally it is found an inch and a half, more rarely two or even three inches, below this point. In [Direction.—Sometimes in man, as is normal in birds, the aorta arches over the root of the right instead of the left lung, and passes down on the right side of the vertebral column; such an arrangement is usually found to be associated with transposition of other viscera. Less frequently, the aorta, after arching over the root of the right lung, is directed to its usual position on the left side of the vertebral column, this peculiarity not being accompanied by any transposition of the viscera. In Conformation.—The aorta occasionally divides, as in some quadrupeds, into an ascending and descending trunk, the former of which is directed vertically upward, and subdivides into three branches, to supply the head and upper extremities. Sometimes the aorta subdivides soon after its origin into two branches, which soon reunite. In one of these cases the oesophagus and trachea were found to pass through the interval left by the division of the aorta; this is the normal condi
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
