(c) The impulse of arteries locally diseased is much better studied by palpation than by the sight.

SECTION II.-APPLICATION OF THE HAND.

The systole of the ventricles conveys to the entire extent of the arterial system an undulatory and somewhat expansible motion (easily felt in vessels, of a certain size, lying within reach of the fingers) known as the arterial pulse or diastole. Each arterial diastole is followed by a contraction or systole. In vessels close to the heart the pulse is perfectly synchronous with the ventricular systole, but falls more and more behind it, in point of time, the further the artery from the central organ. With this qualification, the synchronism of the pulse and ventricular systole is perfect in health; the altered rhythm of the latter, produced by changes of posture (sitting, lying, standing, &c.,) and all other physiological causes, is impressed on the former. In diseases of the heart, various perversions of this synchronism occur, and have been already described.

The characters of the pulse which may have diagnostic signification in cardiac disease are as follow:-the diastole may be quick or slow, short or prolonged, soft or hard, loose or tense, empty or full, small or large, equal or unequal in force, and other characters, in successive beats; and the rhythm may vary in the different forms elsewhere noted (p. 171.) The stroke may be vibratory, jerking, undulatory, bounding, or reduplicate (bis-feriens:) these terms are in themselves sufficiently explanatory of the states to which they refer.

The pulsation of the thoracic aorta can be felt only in one spot in health, above the sternal notch. If the finger be pressed downwards in that position, the patient's head being at the same time bent forwards, slight impulse is, in the majority of cases, detected: where the arch lies high, there will, of course, be very distinct movement. True aortic impulse is felt directly in the middle line; impulse inclined to the right side originates in the innominate artery. The pulsations of the abdominal aorta may be felt, if pressure proportional to the thickness of the parietes, &c., be made with the hand or stethoscope. The movement is simply one of elevation of variable force. Except in very thin persons, it is impossible to feel the beat of the vessel laterally.

In the various forms of dilatation of the arteries, the dilated portion (unless it be more or less completely filled with solidified fibrine) pulsates with undue force. The character of the movement becomes hammering,-its force sufficient, in some cases, to shake the entire trunk and limbs. The pulsation is expansile, as well as heaving, in character; but the distinction of the two movements is not always practically easy. In the case of the thoracic aorta, there is no artifice by which obscure expansile movement may be rendered distinct. In that of the abdominal portion of the vessel, the hands may be sometimes slipped deeply on either side of the vessel, and a double sideward impulsion sometimes detected, which escapes detection when the examination is made in front only. But it must be confessed that the pulsation of the aorta, when pushed forwards by an enlarged vertebra or tumour, cannot always be distinguished by this plan from that of enlargement of the vessel itself.

Arterial pulsation is in various forms of disease accompanied with thrill, occasionally more intense than the valvular variety. Simple dilatation of a vessel, such as the arch of the aorta, especially if it be roughly calcified, is a more efficient cause, than aneurism, of this phenomenon; and a spanæmic state of the blood contributes greatly to intensify it, when other conditions are favourable. Thrill may, in such a combination of circumstances be felt two or three inches beyond the limits of the dilated vessel. Certain morbid states of the blood, especially spanæmia, will suffice, independently of any organic disease, to produce arterial thrill, which, though slighter in amount, is generally more diffused than that of organic origin.

SECTION III.—PERCUSSION.

In the natural state, the thoracic aorta has no influence on the percussion-sound of the surface beneath which it lies. Even where the arch lies high, this resonance at the sternal notch can scarcely be said, practically speaking, to be affected.

But when the vessel is notably dilated, dulness under percussion, of course, occurs, proportional in extent and intensity to the amount of enlargement,-modified in some degree by the fluid or solid state of its contents, and, to a serious degree, by the vicinity of the enlargement to the surface, and the condition of the intervening textures.

The dulness of a saccular dilatation of a vessel is not coextensive with its dimensions. From its more or less globular form, a limited portion only of the sac reaches the chest-walls, and the observer cannot safely percuss with sufficient force to detect its deeply-seated parts. Hence, practically, an intrathoracic, and even an abdominal, aneurismal sac, is always larger than the results of percussion would indicate. In nonsaccular dilatation of the aorta, percussion is, for obvious reasons, a surer guide to the size of the enlargement.

The resistance of a sac filled with fibrine is highly marked; and the deficiency of elasticity so peculiar, as to help in distinguishing the dulness under percussion from that of other states; as, for instance, tuberculization of adjoining lung. The line of union of simply condensed lung and a saccular dilatation is, however, with much difficulty to be drawn, even with the help of this peculiarity.

It is difficult to fix the smallest amount of dilatation of the arch of the aorta that can be clinically demonstrated. Much will depend on the pains taken in the investigation,—much on the thinness of the chest-walls and the healthiness of other parts; but much more on the precise site of the dilatation. In a case where the dilatation increased the width of the vessel, when cut open, by two inches, and hence increased the diameter of the unopened vessel by only about two thirds of an inch, the fact of its existence, suspected from thrill and undue impulse, was proved by percussion. But here the right angle of the arch, the point where the vessel nears the surface most closely, was affected. Such an amount of dilatation could not have been detected in any other part of the arch.* Physical evidence will always be difficult to obtain, where a small sac is situated at the posterior surface of the vessel; but by careful percussion in the course of the arch, a sac as large as a goodsized walnut may be discovered, if it lie any where between the second right interspace and the left border of the sternum.

SECTION IV.—AUSCULTATION.

Two sounds, synchronous with each systole and diastole of the heart, are, in the state of health, clearly audible in the

*H. Gordelier, U. C. H., Males, vol. iii. p. 331, and Consumption Hospital, vol. i. p. 56;-the patient was extremely thin, too; an accidental aid of no mean importance.

course of the pulmonary artery and arch of the aorta: gradually weakening in force in the thoracic division of the latter vessel, they are with difficulty caught in the lumbar region, but by depressing the abdomen with the stethoscope, may readily be heard in front. In some persons, however, a single sound, synchronous with the diastole of the vessel, can alone be detected below the chest.

In the carotid and subclavian arteries almost always, in the axillary and femoral in a fair proportion of cases, the sound continues double; in vessels more remote from the heart, a single sound only, synchronous with the arterial diastole, can be heard. The more active the circulation, the larger the vessel, the thicker its walls (provided their elasticity be not impaired,) the more marked is the sound perceived on auscultation. It is not unusual to find a single (very rarely a double) sound even in the brachial and radial arteries, where these conditions are favourable. In the vicinity of the heart, the arterial sounds closely resemble the cardiac, in quality, pitch, and proportional duration; at a short distance from the heart, both become equalized in length and loudness; sometimes in the carotids the second is the longer and louder of the two.

If the vessels are full, and the blood of natural composition, the arterial sound is duller, but more prolonged, than when the mass of blood is small, and its quality thin. The arterial sounds are louder in females, children, and thin persons, than in males, adults, and stout people. Their intensity is increased by slight pressure; a blowing murmur takes their place, in a large proportion of persons, under stronger pressure.

The arterial sounds heard in the vicinity of the heart are doubtless in great part transmitted from that organ: as the second can rarely be heard at any distance from the heart, the inference indeed arises that it is solely a transmission sound, and that the systole of the arteries (at least of the minor ones) is noiseless. But that the impulsion and friction of the blood against the vessels, and vibrations of their walls, during their diastole, with the current-like motion given to their column of blood by the form of the vessels, generates sound, cannot be doubted; it is not conceivable that sound, audible in the popliteal or radial artery, is the mere result of conduction. Besides, it is not very uncommon to find the first sound in the carotid artery (oftener the right than the left) stronger than at the aortic orifice.

The arteries, like the heart, become the seat of murmurs, either from organic change or independently of this.

(a) Organic murmur in the intra-thoracic arteries varies in intensity from a scarcely perceptible sound to one audible even at a slight distance from the surface; is limited to a small portion, or (more rarely) extends over a considerable tract of the vessel; presents all the varieties of quality noted in cardiac murmurs; varying in pitch from that of the word awe whispered in inspiration, to a high whistling note; is of distinctly intermittent rhythm, single (systolic or diastolic) or double; and either short and abrupt, or prolonged and slow.

The organic conditions of arterial murmur are referrible to (1) change of form of the vessel; (2) to a modified condition of its internal surface; (3) to both these states combined; and (4) to communication between an artery and some portion of the venous system.

(1) General dilatation, or simple lateral sacculation of an artery, especially if abrupt and well-marked, by altering the direction of the blood current, generates murmur, even if the internal surface be perfectly smooth. Narrowing of a vessel produces a similar effect by increasing the friction of the blood against the walls at the constricted point.* Murmur of both these kinds is always synchronous with the pulse, and not rough, unless the blood be spanæmic, and the inner walls deficient in smoothness.

(2) Mere atheroma, unless accumulated in unusually large. quantity, does not produce murmur; infiltration with indurationmatter, by puckering the inner surface irregularly, roughens the sound; erosions of the lining membrane do so more effectually; and calcification of the vessel, if it cause irregular elevations of that membrane, is still more efficient. It seems almost certain that murmur must be produced by particles of exudation-matter studding the surface of an artery recently inflamed; but I have not actually observed the fact. This variety of murmur is always synchronous with the pulse.

(3) In the varieties of aneurism with diseased coats, form and surface are changed so as to produce murmur, which may be systolic, diastolic, or both, and attended or not with sound also. The conditions regulating the time and accompaniments of this murmur, will be described under the head of Aneurism.

* Dr. Corrigan, however, argues with great ingenuity that it is not at the constricted point of a vessel, but in the loose walls beyond, that murmur is produced.