ARTERIES, DISEASES OF. Most of the important morbid conditions of the arteries are those which are occasioned by the deposition of atheroma (a Greek word signifying a tumor or deposit containing matter like athZre, meal or groats) on the free surface of the inner coat of the vessel; a new inner lining to the artery being thus furnished. As atheroma has the effect of weakening, enlarging, and occluding arteries, according the extent and period of the deposition, it is expedient briefly to notice the most important stages of its progress. In the earliest stage, atheroma consists of a thin, soft, and clear membrane, lining a part or the whole of the tube. It seems to be a mere addition to the artery, in whose original coats there is no appearance of disease. It is most probably a deposit on the inner surface from the blood. On the inner surface of the new coat, a similar layer gradually forms, and in course of time, becomes the founda tion of subsequent formations; and when many strata have thus been deposited, the collective mass ceases to be transparent, and becomes converted into an opaque material similar to hardened albumen, and finally to ligament. Until this consolidation occurs. the coats of the artery are not much affected; but by their adhesion to the hardened deposit, they lose their strength, elasticity. and natural color, and their functions are destroyed. The indurated deposit may now undergo one or other of these changes: it may either soften in its interior, in which case it degenerates into a pulpy mass of cholesterins, oil-globules, albuminous and chalky molecules; or it may be converted into a layer of hard, chalky, bone-like matter. This latter change (cretefaction or ossifica tion) takes place only in the external oldest layers of thick deposits; and nothing intervenes between the bony plate and the middle coat of the artery, for the inner or lining coat partakes in the morbid change. It is obvious that either of these changes (softening or hardening) must gradually lead to disease of the arterial coats generally. The process of change is slow, and the change itself can only be detected in the living subject when it is in an advanced stage. In the radial artery and others which lie superficially, the finger can often detect rings or tubes of chalky matter. Most commonly, however, the state of the arteries is detected by some secondary symptom.
Atheromatous deposit is at first attended with a narrowing of the calibre of the vessel, varying with the thickness of the deposit, and most marked at the points of bifurca tion. 'Smaller arteries may be completely obliterated, whilst the larger arteries may be very much Contracted. Thus, the common iliac has been fOthid:Ici have its canal dimin ished by about one half, and the great ascending branches of the arch of the aorta, the subelavian and carotid arteries, have been found very nearly closed. A later conse quence of the same disease is dilatation of the vessel. The power of the outer coats being insufficient to compress the deposit and to close in upon the blood, by which each contraction of the left ventricle of the heart distends them, they remain wide and dis tended during the relaxation of the ventricle, and the artery thus slowly expands; the enlargement being most marked at parts where there is most obstruction to the blood current, as, for example, in curved arteries. These dilatations are apt to terminate in regular aneurism. The changes which we have already described have an effect on the retractile power of the arteries. A healthy artery, if cut across, may shorten to the extent of an inch and a half, as has been actually measured by Mr. Moore (" Diseases of the Arteries," in IIolmes's System of Surgery, vol. iii. p. 329); but the retractile power is destroyed by the deposition of bony rings or plates. But although incapable of short ening, the arteries sometimes become abnormally lengthened, and consequently become not only dilated, but also tortuous. If the outline of superficial arteries thus affected be watched, each pulsation of the heart is seen to increase their curvature; and deep-seated arteries (as the iliac) are thus often forced from their normal positions. Another condi
tion involving much danger is this: an ossified artery loses the smoothness which the interior of the vessel ought to present, and from the displacement or cracking of a bony plate, there may be sharp, rough projections exposed, to which the fibrin of the circu lating blood may adhere. These little clots becoming detached, may be carried with the blood till they become arrested, and plug up an artery, thus presenting cases of embolism or thrombosis (q.v.). Again, the relation of this disease to accidents and sur gical operations on arteries is obvious. A blow may crush a diseased artery, when a healthy elastic vessel might have escaped injury. Such a slight movement as suddenly lifting the arm to the head, for the purpose of securing the hat in a sharp gale, has been known to have been followed by aneurism of the axillary artery. A ligature applied to any ossified artery, is very apt to cause it o break, and the difficulty of securing such vessels is often very great. It is to thi form of disease that most of the failures of operations for aneurism are due. Hav ig thus noticed the most important changes which are induced in the arteries by athe mut, and the evil consequences to which they may give rise, we shall now direct attention to an important cause of occlusion—that, namely, in which the canal is closed by an imported foreign body, and especially by fibrinous plugs originally formed in the heart, and transported to other parts in the stream of the blood. When a large artery, as, for example, the principal artery of one of the limbs, is " suddenly plugged in its higher part, a sensation of severe pain is com monly the immediate result of the accident. In some cases, the pain extends along the course of the vessel, which, though pulscless, is extremely tender; in others, the suffer ing is referred to sonic distant part of the limb, as, for instance to the calf. Signs of a deficient circulation succeed, and they may amount to pallor, loss of temperature, numb ness of the surface, or even to that ' torpor ' which is observed to precede the total death of a limb in certain cases of injuries of vessels. Such torpor implies not only a loss of circulating blood, but also a cessation of all feeling and motor power in the limb." —Moore, op. cit., p. 835. Although gangrene (q.v.) is always to be feared as the result of an obstructed artery of large size, it does not invariably follow; as a collateral circulation may be established, and the life of the limb may be thus saved. Very young persons will endure the obliteration of very large vessels without gangrene;' and a case is on record (.lied. Chir. Trans., vol. xxix. p. 214) in which "all the main arteries of both upper extremities and of the left side of the neck were reduced to solid cords," and yet no gangrene ensued. From the description of the symptoms, the nature of a case of sudden occlusion of a large artery by a plug may possibly be recognized, or, at all events, suspected even by a non-professional observer. Medical aid must at once be sought. The early indications of treatment are to preserve the temperature of the part, to favor the establishment of a collateral circulation, to protect the limb from irritation or injury, to give nourishing blood-making food, and to relieve pain by the judicious use of opiates. The later treatment, if the affection is not checked, is that which is described in the article GANGEENE.—Arteriti$, or inflammation of the arteries, was a disease which was formerly recognized by physicians. • No such specific general disease is now believed in ; but the changes which have been already described as occurring in consoli dated atheromatous deposits—either softening or ossification—are accompanied by an unnaturally vascular condition of the attenuated arterial walls, extending to true local inflammation, and even to suppuration.—Aneurism (a tumor containing blood, and com municating with the cavity of an artery) has been considered in a special article.