626 THE AORTA. 



tained in reference to the origin of these sounds, which it is 

 not thought necessary to notice further in a work like the 

 present. 



THE AORTA, (Fig. 8.) 



The origin, course, and termination of the aorta, together 

 with a general outline of its primary and prominent sec- 

 ondary branches, will he found under the head of the vas- 

 cular tissue. A detail of the several branches, supplying 

 the various organs contained in the cranial, abdominal, 

 and thoracic cavities, the exceptions hereafter to be no- 

 ticed, have also been given in connection with the exam- 

 ination of each of these organs. So that all we propose, 

 in the present place is, a brief recapitulation of the primary 

 branches of the aorta, in the order in which they suc- 

 cessively arise from this tube, and the organs and vis- 

 cera to which they are respectively distributed, so as to 

 fix, more firmly in the memory, the chain of connection 

 between these two great classes of organs, and their relative 

 dependency. 



The aorta, it is known, comprises the great trunk or 

 arterial half of the general or systemic circulation. Com- 

 mencing in the upper portion of the left ventricle of the 

 heart, concealed by the pulmonary artery, it ascends to the 

 right side, on a level with the second rib and its cartilage; 

 then crosses behind the sternum, about an inch below its 

 upper edge, to the left side, when it turns downward and 

 inward to the third or fourth dorsal vertebra. To this 

 point a curvature is described, constituting the arch of the 

 aorta, which consists of an ascending, transverse, and de- 

 scending portion. From the arch, the aorta continues 

 descending upon the left side of the vertebral column, 

 through the thoracic cavity, to the diaphragm, to which 

 point it is called thoracic aorta. Passing beneath the crura 

 of the diaphragm, it enters the abdomen and traverses this 

 cavity upon the median line, to the space between the 

 fourth and fifth lumbar vertebras, where it terminates by 

 dividing into the common or primitive iliac arteries. 



