The progress of natural cure is indicated by the aneurysm becoming smaller, firmer, less expansile, and less compressible; the murmur and thrill diminish and the pressure effects become less marked.  When the cure is complete the expansile pulsation is lost, and there remains a firm swelling attached to the vessel (consolidated aneurysm).  While these changes are taking place the collateral arteries become enlarged, and an anastomotic circulation is established.

An aneurysm may prove fatal by exerting pressure on important structures, by causing syncope, by rupture, or from the occurrence of suppuration. Pressure symptoms are usually most serious from aneurysms situated in the neck, thorax, or skull.  Sudden fatal syncope is not infrequent in cases of aneurysm of the thoracic aorta.

Rupture may take place through the skin, on a mucous or serous surface, or into the cellular tissue.  The first haemorrhage is often slight and stops naturally, but it soon recurs, and is so profuse, especially when the blood escapes externally, that it rapidly proves fatal.  When the bleeding takes place into the cellular tissue, the aneurysm is said to become diffused, and the extravasated blood spreads widely through the tissues, exerting great pressure on the surrounding structures.

The clinical features associated with rupture are sudden and severe pain in the part, and the patient becomes pale, cold, and faint.  If a comparatively small escape of blood takes place into the tissues, the sudden alteration in the size, shape, and tension of the aneurysm, together with loss of pulsation, may be the only local signs.  When the bleeding is profuse, however, the parts beyond the aneurysm become greatly swollen, livid, and cold, and the pulse beyond is completely lost.  The arrest of the blood supply may result in gangrene.  Sometimes the pressure of the extravasated blood causes the skin to slough and, later, give way, and fatal haemorrhage results.

The treatment is carried out on the same lines as for a ruptured artery (p. 261), it being remembered, however, that the artery is diseased and does not lend itself to reconstructive procedures.

Suppuration may occur in the vicinity of an aneurysm, and the aneurysm may burst into the abscess which forms, so that when the latter points the pus is mixed with broken-down blood-clot, and finally free haemorrhage takes place.  It has more than once happened that a surgeon has incised such an abscess without having recognised its association with aneurysm, with tragic results.

#Treatment.#—­In treating an aneurysm, the indications are to imitate Nature’s method of cure by means of laminated clot.