1108 Dilatation of the Aorta. 



have formed on the abdominal aorta can be palpated, in larger 

 animals from the rectum, in smaller animals through the abdom- 

 inal wall. Below the vertebral column, slightly to the left, a 

 pulsating swelling is felt, of variable size, elongated or spherical, 

 firm or slightly elastic, which is continued into the normal seg- 

 ment of the aorta or into the two pelvic arteries. Sometimes 

 the character of the swelling cannot be determined exactly ; that 

 is in cases in which edematous swellings or tough connective 

 tissue have formed around it. 



The pulsation of the swelling does not, of itself, prove the presence of an 

 aneurysm, because tumors or abscesses connected with the aorta may show a similar 

 pulsation, although it is then only by continuation. If it can however be determined 

 by grasping the swelling, that it becomes harder and larger with each pulsation, 

 an aneurysm is undoubtedly present. 



An important symptom is presented by the retardation and 

 sluggishness of the pulse, which may, however, be observed only 

 in case of a considerable thrombosis. The pulse is felt dis- 

 tinctly after the heart beat, distally to the dilatation, because 

 the copious deposit of fibrin has usually made the lumen 

 of the vessel narrower and has thereby impeded the flow of blood 

 toward the periphery; in consequence the increase in the sys- 

 tolic blood pressure, which is recognized as a pulse beat, reaches 

 its climax, in which it can be felt, later. The vessels in which 

 this retardation can be felt depend, of course, upon the situa- 

 tion of the aneurysm. If this is at the origin of the aorta, the 

 retardation is noticed in all arteries of the body, an aneurysm 

 in the posterior aorta causes a retardation of the pulse only in 

 the arteries of the posterior half of the body It may also occur 

 that the pulse is not synchronous in the two corresponding lat- 

 eral halves of the body, viz., if an artery branching out from 

 the aneurysm has become narrower. 



Over aneurysms which lie superficially or which form on 

 the aorta, vascular murmurs are usually heard, which may be 

 perceived as either one or two murmurs or as*a continued roar- 

 ing. Over a pulsating swelling in the sacral region Tombari 

 heard a blowing murmur, which had more the character of rub- 

 bing, while over a dilatation of the first segment of the pos- 

 terior aorta Schmidt perceived a humming sound which was 

 synchronous with the heart beat. In aneurysms at the origin 

 of the aorta the murmurs are heard over the base of the heart 

 and even lower down. 



The left half of the heart is hypertrophied only in those 

 eases in which extensive arteriosclerosis is present at the same 

 time as the aneurysm or in which the lumen of the dilated aorta 

 has become much narrower on account of thrombi. A dilata- 

 tion at the origin of the aorta may lead to insufficiency of the 

 semilunar aortic valves. 



In case of considerable stenosis of the vascular lumen the 

 nutrition of the parts of the body which are distal to the dilata- 



