#Clinical Features of Aneurysm.#--Surgically, the sacculated is by far the most important variety. The outstanding feature is the existence in the line of an artery of a globular swelling, which pulsates. The pulsation is of an expansile character, which is detected by observing that when both hands are placed over the swelling they are separated with each beat of the heart. If the main artery be compressed on the cardiac side of the swelling, the pulsation is arrested and the tumour becomes smaller and less tense, and it may be still further reduced in size by gentle pressure being made over it so as to empty it of fluid blood. On allowing the blood again to flow through the artery, the pulsation returns at once, but several beats are required before the sac regains its former size. In most cases a distinct thrill is felt on placing the hand over the swelling, and a blowing, systolic murmur may be heard with the stethoscope. It is to be borne in mind that occasionally, when the interchange of blood between an aneurysm and the artery from which it arises is small, pulsation and bruit may be slight or even absent. This is also the case when the sac contains a considerable quantity of clot. When it becomes filled with clot--_consolidated aneurysm_--these signs disappear, and the clinical features are those of a solid tumour lying in contact with an artery, and transmitting its pulsation. A comparison of the pulse in the artery beyond the seat of the aneurysm with that in the corresponding artery on the healthy side, shows that on the affected side the wave is smaller in volume, and delayed in time. A pulse tracing shows that the normal impulse and dicrotic waves are lost, and that the force and rapidity of the tidal wave are diminished. [Illustration: FIG. 71.--Radiogram of Aneurysm of Aorta, showing laminated clot and erosion of bodies of vertebræ. The intervertebral discs are intact.] An aneurysm exerts pressure on the surrounding structures, which are usually thickened and adherent to it and to one another. Adjacent veins may be so compressed that congestion and œdema of the parts beyond are produced. Pain, disturbances of sensation, and muscular paralyses may result from pressure on nerves. Such bones as the sternum and vertebræ undergo erosion and are absorbed by the gradually increasing pressure of the aneurysm. Cartilage, on the other hand, being elastic, yields before the pressure, so that the intervertebral discs or the costal cartilages may escape while the adjacent bones are destroyed (Fig. 71). The skin over the tumour becomes thinned and stretched, until finally a slough forms, and when it separates hæmorrhage takes place. [Illustration: FIG. 72.--Sacculated Aneurysm of Abdominal Aorta nearly filled with laminated clot. Note greater density of clot towards periphery.]