270 CLINICAL APPLIED ANATOMY. 



present in the second interspace of the left side, especially if 

 they arise very near the origin of the aorta. They have also 

 been known to separate the manubrium from the gladiolus, a 

 process which is facilitated by the normal presence of a cartil- 

 aginous connection between these two parts of the sternum and 

 the occasional presence of a synovial cavity. 



The superior vena cava and the right auricular appendix are 

 closely applied to the right side of the ascending aorta. The 

 cava is sometimes perforated by an aneurysm, giving rise to 

 highly characteristic symptoms and signs. These consist of 

 sudden pain, followed by cyanosis and oedema of the head, neck 

 and arms, the development of a continuous murmur running 

 through systole into diastole, and the presence of a local thrill. 

 When the superior cava is compressed, the resulting lividity and 

 oedema are restricted to the head, neck and arms, but should 

 the pressure be proximal to the point of entrance of the great 

 azygos vein, the chest will also share in the congestion. 



An incomplete spiral around the ascending aorta is formed by 

 the pulmonary artery and its right main subdivision. The com- 

 mencement of the pulmonary artery lies in front of the aorta, 

 the main pulmonary trunk is closely applied to the left side of 

 the vessel, and the right branch passes behind it. The relations 

 of the vessels being so intimate, the pulmonary artery is liable 

 to compression by aneurysms of the ascending aorta. These 

 aneurysms sometimes rupture into the pulmonary artery. Sudden 

 pain, with the development of a continuous murmur, signalise 

 this accident, but oedema, such as occurs when the superior vena 

 cava is similarly perforated, rarely occurs. The right bronchus 

 is more or less separated from the aorta by the right pulmonary 

 artery, but may, like the latter, be subjected to pressure with 

 resulting secondary changes in the right lung. The right lung 

 itself is only separated from the aorta by the superior vena cava 

 and so may be subjected to direct pressure by the aneurysm. 

 The right phrenic nerve lies on the right side of the superior 

 vena cava, and may also be implicated. 



Aneurysms at the junction of the ascending and transverse 



