TJioracic Aneurysm 181 



arch is lengthened and the heart lowered, and the struggling left 

 ventricle is considerably enlarged. Circulation is delayed, and, an 

 imperfect supply of blood passing to the lungs, shortness of breath is 

 usually a prominent sign. 



If the tumour happen to press upon and irritate a sympathetic 

 chain there may be dilatation of the pupil of that side (p. 88) ; contrac- 

 tion of the pupil suggests that the pressure is severe enough to paralyse 

 the sympathetic. In any case, the aneurysm is apt to cause inequality 

 of the pupils. 



In aneurysm of the aortic arch the pulsation is exactly synchronous 

 with ventricular contraction ; and there may be a quiet space between 

 the region of the cardiac impulse and the abnormal pulsation. In 

 examining the tumour one hand should be placed flat over the pulsa- 

 ting area in front, whilst the other is laid between the shoulders during 

 expiration ; in this way the characteristic expansion may be best de- 

 tected. The sac may burst externally, or into the pericardium, pleura, 

 lung, trachea, cesophagus, mediastinum, spinal canal, or even into the 

 pulmonary artery itself. 



Sometimes the chief and most characteristic symptom of the disease 

 is pain down the left arm, or at the left shoulder an important clinical 

 fact which anatomy fails at present efficiently to explain. 



Aneurysm of the first part is of the most frequent occurrence 

 perhaps, as already remarked, because the second and third portions are 

 strengthened by the fibrous element of the pericardium. Another ex- 

 planation is that the blood from the left ventricle is, on account of 

 the obliquity of the heart, pumped forcibly against the outer side 

 of the first part, which it gradually stretches and weakens. The 

 aneurysm begins as a pulsating tumour in the second right space, close 

 to the sternum ; the apex-beat being displaced towards the left side. 

 The dilatation is apt to start in a sinus of Valsalva, the right for choice, 

 and it is, therefore, usually sacculated. 



Aneurysm of the first part of the arch may press upon the superior 

 vena cava, and cause venous congestion of both sides of the head and 

 neck, and of both upper extremities ; indeed, a case is recorded by 

 Watson in which almost the whole of the blood coming from the head 

 and arms was returned by dilated epigastric veins into the external 

 iliacs, to reach the heart by the inferior cava. The obstructed return 

 of blood from the brain causes dizziness and headache. 



Bulging backwards against the root of the right lung, the tumour 

 may obstruct the bronchus; and, pressing against the pulmonary artery, 

 it may cause a systolic bruit. Sometimes it produces absorption of the 

 ribs and sternum, and bursts at last into the pericardium, pulmonary 

 artery, or pleura, or through the thinning integument. 



Aneurysm of the transverse aorta forms a pulsating tumour behind 

 the manubrium \vhich may even extend to the left of that bone. It may 

 press upon the trachea and cause dyspncea, cough, and harsh breathing; 



