240 « THE AORTA. 



CHAPTER VIII. 



A PARTICULAR ACCOUNT OF THE DISTRIBUTION OF THE AR- 

 TERIES. 



Of the Aorta,* or the Great Trunk of the Arterial System. 



When the heart is in its natural position, the right ventricle 

 is nearly anterior to the left, and therefore, the Aorta, where it 

 originates from the left ventricle, is behind the pulmonary 

 artery, and covered by it. Its first direction is so oblique 

 towards the right side of the body, that it crosses the pulmonary 

 artery behind, and appears on the right side of it. It has 

 scarcely assumed this position before its course alters, for it then 

 proceeds obliquely backwards and to the left ; so as to form a 

 large curve or arch, which extends to the left of the spine. 



The position of this curve or arch is so oblique, with respect 

 to the body, that the cord or diameter of it, if it were extended 

 anteriorly and posteriorly, would strike the cartilage of the 

 third right rib about the middle of its length, and the third 

 left rib near the head. In consequence of this position of the 

 curve, the Aorta crosses over the right branch of the 

 pulmonary artery, and the left branch of the windpipe : and as- 

 sumes a situation, in front, and to the left of the third dorsal verte- 

 bra : from this situation it proceeds downwards : in front, but rather 

 on the left side of the spine, and in contact with that column.f 



* This name was given by Aristotle. — h. 



f In a case which I recently examined, I found the position of all the 

 thoracic and abdominal viscera, reversed from side to side. — The right lung had 

 three lobes and the left two ; the heart was turned to the right side of the tho- 

 rax, and the venous ventricle and auricle were found on the left side of the organ. 

 The arch of the aorta was turned from the left to the right side, and the 

 arteria innominata was sent up on the left side of the neck. — The aorta 

 pursued its course down on the right side of the spinal column with the vena 

 cava to its left. The spleen, the cardiac orifice of the stomach, the small lobe 

 of the liver and the sigmoid flexure of the colon were on the right side ; the 

 large lobe of the liver and the gall bladder, with the pyloric orifice of the 

 stomach, and the ccecum were found upon the left. — p. 



