158 Anatomy Applied to Medicine and Surgery. 



of a peculiar harsh sound, heard, at first, in inspiration only, 

 but, later on, in expiration as well. If it be the trachea 

 that is compressed this abnormal sound will be heard 

 over both lungs equally, but, if the pressure be on a bron- 

 chus, then the sounds will be heard over the corresponding 

 lung only. In dyspnoea, from such diseases as 

 asthma, etc., the patient will sit as upright as possible and 

 with his head thrown back, but, in dyspnoea from thora- 

 cic aneurism, the position assumed is generally with the 

 head forward, as in resting the head on the folded arms on 

 a table, the reason being, that the aneurism presses more 

 on the trachea or bronchus in the recumbent than in the 

 upright position, and hence the patient leans forward to 

 lessen the pressure on these structures. A lesser degree 

 of dyspnoea may be the result of irritation of one recurrent 

 laryngeal nerve, by the aneurism, and this would cause a 

 spasm of one side of the glottis, but, if both nerves be ir- 

 ritated, then the dyspnoea would be extreme. 



4. Effects on the Pulse. Normally the radial 

 pulse is one-tenth of a second later than the ventricular 

 impulse, but, should the aneurism affect the innominate 

 artery only, then the right radial pulse would be delayed 

 for a slightly longer period than normal. Should, how- 

 ever, the aneurism affect the left subclavian alone, then 

 the left pulse, only, would be delayed, whereas, if both 

 pulse be delayed, it is probable that it is the ascending 

 part of the aorta that is involved. If both pulse be af- 

 fected, with the right more than the left, then, it is prob- 

 able that the innominate and aorta, together, are the 

 vessels affected. 



5. Pressure on the Veins. Should the lower 

 half of the superior vena cava be compressed, there would 

 result a certain amount of cyanosis of the head, neck and 

 upper limbs, the superficial veins becoming distinct and 



