senile decay of the tissues. But there are not sufficient grounds for this opinion. Many of the most remarkable instances of degeneration of the coats of the aorta which have come under under my notice have been in persons not yet passed the prime of life; and aneurism, which is a form of disease essentially connected with these structural changes in the artery, is more common before than after the age of fifty. Therefore it must be admitted that although degeneration of the coats of the arteries, like degeneration of other tissues of the body, is most liable to occur in advanced life, yet that the causes which set it in operation may be fully developed at almost any period of man's existence.

The results which flow from this form of disease are of great practical importance. The loss of elasticity and contractility of the artery consequent on the altered structure of its coats may cause it to yield to the dilating force of the blood thrown into it at each systole of the heart, and so to become permanently dilated and enlarged; its loss of elasticity, by increasing the resistance to the stream of blood, and its loss of contractility, by impairing its power of propulsion, may impede the arterial circulation, throw additional labour on the heart, and give rise to hypertrophy, or to hypertrophy and dilatation of that organ; the roughening of its internal surface may occasion a murmur synchronous with the systole of the heart, and the brittleness of its coats may prepare the way for the occurrence of aneurism.

Dilatation sometimes affects the whole circumference of the aorta, so that the artery is uniformly enlarged, but, very commonly, the dilatation is more marked in the anterior and right portion of the ascending aorta, and in the upper surface of the transverse portion of the arch-the parts against which the current of the blood is directed with the greatest force; and sometimes the dilatation is even more circumscribed, and assumes a sacculated form, so that distinct pouches project from the external surface of the vessel, in consequence of the coats having yielded more rapidly at some points than at others. These pouches form the commencement of that variety of disease to which the title of aneurism has been applied.

Considerable dilatation and roughening of the coats of the aorta may take place without occasioning murmur; nay, more, the vessel may be sacculated, and may even present a distinct aneurismal pouch, without proving the source of murmur.* This is partly dependent on the

*This fact may be illustrated by reference to the case of James Howard, aged thirty-four, who was admitted under my care in the King's Ward of St. George's

character of the blood, and the nature of the roughening; partly on the force of the blood's current, and partly on the particular portion of the vessel, which happens to be the seat of roughening and dilatation. If the circulation be languid, the blood healthy, the roughening extensive, rather than prominent, and the seat of roughening such that the current of the blood is not directed against it, there may not be, and, probably, will not be a murmur. But, when on the other hand, the blood is anæmic or spanæmic, and the circulation active, and when the current of the blood is directed against a portion of the vessel at which there exists a distinct prominence or roughness of a nature to cause a forcible eddying of the blood, a murmur can scarcely fail to accompany each systole of the heart.

In many of these instances the aortic valves are thickened, and give rise to a systolic murmur, which it is difficult to distinguish from the murmur occasioned by dilatation and roughening of the aorta; but when a murmur is due to the latter cause alone, it will usually be heard louder at the second right cartilage and in the track of the aorta than it is over the semilunar valves, and not unfrequently the pulsation and thrill of the dilated aorta will be felt on placing the finger above the sternal notch, and pressing it downwards, behind the sternum. Sometimes, indeed, the pulsation may be seen as well as felt above the sternal notch, and also above the clavicles, and the murmur audible over the arch of the aorta is propagated along the great vessels in the neck.

When pulsation and thrill are clearly perceptible above the sternal notch, and also in the large vessels of the neck, a suspicion of sacculated aneurism may often arise, and the diagnosis may not be easy. Simple non-sacculated dilatation of the aorta, especially when the internal surface of the vessel is roughly calcified, may give rise to the most intense

Hospital, on April 2nd, 1862. This man had an aneurism the size of a large orange which sprang from a part of the ascending and transverse portions of the arch, and involved the origin of the arteria innominata. This aneurism had pushed its way forward, had caused erosion of the sternum, and presented itself superficially as a pulsating tumour. On dissection, the aneurismal sac just referred to was found half filled with old laminated fibrin, the aorta was extensively diseased in other parts besides that which formed the seat of the aneurism, and at about an inch above the semilunar valves there was a large empty pouch about the size of a hen's egg which had a smooth opening into the aorta about the size of a shilling. Yet, in this case, during the whole time that the patient was under observation there was not the slightest roughness or murmur, either over the aortic valves, in the track of the aorta, or over the aneurismal tumour For full details of the case, see The Post-mortem and Case Book' for April, 1862, in the museum of St. George's Hospital.

pulsation, thrill, and corresponding murmur, which, even under ordinary circumstances, may be felt and heard an inch or more beyond the limits of the dilated vessel; and when these phenomena are intensified by the existence of anæmia or spanæmia, or by nervous excitement, it is difficult, if not impossible, to determine at one examination whether circumscribed or aneurismal dilatation of the vessel exists. But careful and repeated examinations will seldom fail to settle the question. If sacculated aneurism exists in a position and of an extent to cause pulsation and thrill on the parts above referred to, percussion could scarcely fail to indicate the fact, nor could there fail to arise, within a limited period, some signs of pressure referable to the aneurismal sac. These of course would be absent if the symptoms were due to simple peripheric dilatation of the vessel.

Aneurism of the Aorta.

Aneurism of the aorta may be defined as a circumscribed dilatation of an artery, consequent on disease in one or more of its coats. Its local character, and that alone, distinguishes it from simple dilatation of the aorta, with which it is pathologically allied. For whether the vessel be generally dilated, or whether its coats have yielded to pressure at one or more points, the change is referable to the impaired elasticity and altered character of the tissues of which the vessel is composed. And, inasmuch as the conditions which produce these alterations in the coats of a vessel do not operate on the aorta alone, but exert their influence throughout the entire system, aneurism of the aorta is usually found associated with a diseased condition of the other arteries.

Thoracic aneurisms are of different varieties and different forms, and occur at different parts of the thoracic aorta.

The three coats of the vessel altered in structure, and less elastic than in health, may remain unbroken, and, yielding under the pressure of the blood from within, may constitute the walls of the aneurismal pouch; or the inner, or the middle, or the outer tunic may give way, leaving the other two coats to form the covering of the tumour; or the two inner coats of the vessels may be ruptured, and the outer tunic only may form the covering of the sac; or yet, again, the two inner coats may crack or rupture, and blood, escaping through the fissures, may separate the outer from the middle tunic, producing a so-called “ dissecting aneu

rism."

Practically, however, these anatomical divisions of aneurismal tumours are of little value; for not only may one variety merge into another as the disease progresses, but the symptoms they severally produce are seldom distinguishable during life. In all cases the whole of the tunics of the artery may be ultimately destroyed, and the walls of the tumour may consist of nothing more than the condensed tissue of the parts on which the aneurism presses.

The forms which aneurismal swellings assume are various, and so also are the sizes to which they attain. The swelling may involve the whole circumference of the vessel, or it may arise from one part only of its walls, the opening into the aneurismal sac being often no larger than a shilling; it may be fusiform or globular, or simply sacculated, or it may be irregularly sacculated, and its size may vary from that of a walnut to the bulk of a child's head.

The contents of the sac are also varied. They may consist entirely of solid fibrin, which is usually found in a laminated form, or they may be wholly fluid; but more commonly they are partly solid and partly fluid, the sac being lined by layers of fibrin which are firmer and denser in proportion as they are nearer to the walls of the sac, and soft and loose textured, and scarcely decolourised where they are in contact with the blood. The firmer the fibrin, and the more thickly it lines the cavity, the greater the strength it affords to the sac, and the less rapid is the progress of the disease; so that in some instances, in which the tendency to the firm coagulation of fibrin is great, the sac becomes nearly filled by coagula, the tumour is rendered solid and resistent, the tendency to further enlargement is stayed, and the aneurism is cured.t

Thoracic aneurisms arise most commonly from the ascending portions of the arch of the aorta, less frequently from the transverse portion of the arch, still less frequently from its descending portion, and quite as seldom from the descending thoracic aorta below the arch. This is explicable by the fact that the commencing portion of the aorta is that on

* For full particulars of a remarkable case of dissecting aneurism of the aorta which fell under my care in St. George's Hospital, in the person of Felix Ridout, aged thirty-two, see Hospital 'Post-mortem and Case Book' for December, 1861. The preparation is preserved in the museum of the hospital.

+ For details of a case in which two aneurisms existed in one patient and were cured spontaneously, see 'Trans. Path. Soc., vol. ix, p. 167. Other cases of spontaneous cure are recorded in the Post-mortem and Case-books,' for 1854 and 1855, in the museum of St. George's Hospital.

which atheromatous and calcareous degeneration of the coats of the vessel most frequently takes place, and in which the strain of the impulsive action of the heart is necessarily most felt. Dr. Sibson,* who has taken infinite pains in collecting and analysing cases of thoracic aneurism, informs us that amongst 703 cases, of which he obtained the histories, or found specimens in various museums, no less than 87 were instances of aneurism of the sinuses of Valsalva, 193† of the ascending aorta alone, 112 of the ascending and transverse portions of the arch conjointly, and 28 of the entire arch; so that some portion of the ascending aorta was involved in no less than 420 cases, or in considerably more than half of the whole; whilst the transverse portion of the arch was affected alone in 120 cases, and conjointly with the descending aorta in 20 cases; the descending part of the arch alone in 72 cases; the descending thoracic aorta below the arch in 71 cases.

There is yet another point of considerable interest in connection with the origin of aneurismal tumours. It has long been noticed that they do not arise indifferently from all parts of the circumference of the aorta, but spring most frequently from those parts of the vessel against which the current of the blood is more particularly directed. In this respect they follow a law which is in constant operation in all rivers, and leads to the pouchings or aneurismal dilatations so constantly observed on their banks. The extent to which this law determines the position of aneurisms is clearly shown by Dr. Sibson's statistics. He informs us that aneurisms of the sinuses of Valsalva most frequently effect the right coronary sinus, and least frequently implicate the left ; that in fifteen instances aneurism of the ascending aorta originated in the anterior aspect of the aorta, in 46 in the right, and in 8 only in the left side, and that in 19 cases the upper aspect of the transverse aorta was the seat of aneurism; its posterior, or, more properly, its right aspect in 41; and its anterior, or, more properly, its left aspect in 19 These facts are important in a practical point of view; for when once aneurismal dilatation has commenced, the tendency of the tumour would naturally be to increase in the direction in which the vessel has yielded, and the only means by which that tendency would be modified is the existence of mechanical obstacles to its enlargement in that direction; and as the organs which present the obstacles to its extension

cases.

* For full statistical details respecting thoracic aneurism, see Dr. Sibson's 'Medical Anatomy,' Fasc. v.

+ Of these 193 no less than 52 were examples of dissecting aneurism.