ANEURISM OF THE AORTA. 421 



the wall of the chest, occurs either by gradual atrophy and final lacera- 

 tion of the integument, or else, which is most common, by loosening 

 and detachment of a slough induced by immoderate and incessant 

 strain. 



Aneurism of the aorta is most frequently situated upon its ascend- 

 ing branch, before the departure of the innominata, and is more com- 

 mon upon its convex than upon its concave side. Those which arise 

 outside of the pericardium, and which are generally very large, usually 

 project toward the right half of the sternum, and become visible in the 

 region of the upper ribs, and costal cartilages of the right side. In 

 the majority of cases, they break into the right pleural sac, or else 

 burst externally. Aneurisms which spring from the concavity of the 

 ascending aorta grow in the direction of the trunk of the pulmonary 

 artery, or toward the right auricle, which they may perforate. Those 

 which arise from the convexity of the arch also extend to the right, 

 forward, and upward, and make then* appearance in the neighborhood 

 of the right sterno-clavicular articulation. Those which proceed from 

 the concavity of the arch press upon the trachea, the bronchi, and the 

 oesophagus, which they may perforate. Aneurisms of the descending 

 limb of the aorta often compress the left bronchus, more rarely the 

 resophagus, and usually open into the left pleural cavity; they may 

 destroy the back-bone, and may come to the surface at the left side of 

 the back. Aneurisms of the abdominal artery often attain an immense 

 size, may also erode the spinal column, and burst into the peritonseum 

 or retroperitoneal connective tissue. 



SYMPTOMS AND COURSE. Persons suffering from aneurism of the 

 aorta often perish suddenly and unexpectedly of internal haemorrhage, 

 before the disease has given rise to any great degree of distress. At 

 other times the symptoms are so obscure as to render a positive diag- 

 nosis impossible. In other instances, again, it admits of a more or less 

 certain recognition from the subjective and objective manifestations 

 which it occasions. 



The signs to which aortic aneurism gives rise depend, in part, upon 

 the crowding and compression of the adjacent organs in the thorax, 

 as described in a previous section ; and in part, also, upon obstruction 

 of the circulation, which is one of the necessary consequences of any 

 large aneurism. 



As a result of compression of the lung or greater bronchi, dyspnoea 

 arises, which is often extremely severe. The most intense dyspnoea, 

 accompanied by a peculiar whistling upon breathing and coughing, 

 attends aneurism of the arch pressing upon the trachea. If the pneu- 

 mogastric nerve or its recurrent branch be stretched or irritated, the 

 dyspnoea may assume a spasmodic, asthmatic character, and appears 



