exocardial or endocardial origin, or, in other words, whether it be a pericardial friction sound or an endocardial valvular murmur.

By what means, then, can a decision be arrived at ? There is no one character by which the true source of the murmur can be recognised; but there are several circumstances which, viewed collectively, will rarely fail to lead to a correct diagnosis. Thus, whilst exocardial murmurs are generally of a rubbing quality, endocardial murmurs are essentially of a blowing character. Exocardial murmurs usually convey the impression of being more superficial in situation than endocardial murmurs; their seat of maximum intensity does not correspond with that of endocardial murmurs; their force does not vary, as they are traced from point to point after the manner of endocardial murmurs; but, on the contrary, they are often limited to one spot, and they are not propagated along the course of the great vessels as are some of the endocardial murmurs. They are apt to vary from day to day, or even from hour to hour in their character, intensity, and position, and not unfrequently are more marked when the patient leans forward, or, if the patient be young and the cartilages of the ribs elastic, when forcible pressure is exerted on the chest walls by means of the stethoscope. They continue throughout the whole period of the heart's action, and therefore, are seldom perfectly synchronous with the sounds of the heart, but appear to begin before, or else to follow at an appreciable interval after the ventricular systole, and they are apt to cease, after a time recommence, and ultimately disappear in a manner which is never noticed in the case of murmur resulting from endocardial mischief. The heart's sounds are more muffled and appear more distant than in the case of endocardial disease, and the lungs being pushed aside by the distended pericardium, the space over which the respiratory sounds are inaudible is wider than when the heart is hypertrophied, as a result of valvular mischief.

Thus, then, it will be admitted that auscultation alone affords many means of distinguishing between exocardial and endocardial murmurs, and when to these are added the existence of friction fremitus, of dulness on percussion in the pericardial region, and of other signs which other methods of examination enable us to recognise, it will be apparent that in the majority of cases inattention alone can lead to difficulty in diagnosing the true nature of the murmur. Nevertheless, when the murmur is single and confined to the systole of the heart, or is simply clicking in its character, the diagnosis is extremely difficult, and, at a

first examination, is almost impossible. But even in these cases the variableness of the signs observed day by day cannot fail within a very short time to point to a correct conclusion.

Pericardial friction varies greatly in duration. It may cease after it has existed for a few hours only, in consequence of adhesion of the two roughened surfaces, or it may endure for many weeks if not for months, especially about the root of the great vessels.* More commonly it continues for several days, is then checked by the outpouring of serous exudation in amount sufficient to separate the two layers of the pericardium, and when it reappears after the absorption of this fluid it ordinarily continues about a week or ten days.

Pericardial friction may be limited to one portion of the pericardial membrane or may extend over its entire surface, and the area over which the friction sound can be heard will vary in a corresponding degree. When the entire surface is affected and has only recently become so, the friction sound is usually heard of maximum intensity towards the apex where the heart is uncovered by lung; but when inflammation has existed for some time and has led to copious effusion into the pericardium, not only are the edges of the lungs pushed aside, but, if the patient be in a semi-recumbent posture, the fluid will gravitate towards the apex of the heart, and under those circumstances the friction sound will be heard of maximum intensity at the base.

It has been attempted to determine the amount and nature of the effusion into the pericardium by reference to the extent and character of the murmur. But observation has proved the impossibility of doing So. The friction sound is more influenced by the energy of the heart's action, and by the extent of movement between the two surfaces of the pericardium, than it is by the mere amount or character of the exudation. So, when the heart is contracting vehemently, a slight amount of exuded lymph will often occasion more intense friction sound, than a much larger quantity of exudation when the systole of the heart is weak.

In some instances, a murmur referable to pleural friction is caused by the action of the healthy heart, and being necessarily cardiac * Dr. Walshe (loc. cit., p. 258) reports a case in which friction sound was audible at the "lower part of the sternum" for upwards of three months, "long after the man's discharge from hospital and apparent restoration to health." I have never met with such a case, nor can I find a record of any other; and I am inclined to doubt whether in the instance referred to by Dr. Walshe the sound may not have been of endocardial origin.

in rhythm, it is apt to be mistaken for pericardial friction sound. But there are several circumstances which ought to excite suspicion as to its origin, and when suspicion is aroused, the diagnosis is seldom difficult. Thus, the murmur does not extend over the præcordial region, but is limited to its confines, and usually remains fixed about its left border; it is commonly accompanied by the signs of pleurisy at the back of the chest, and it ceases, or nearly so, when the patient holds his breath-an act which does not check the continuance of pericardial friction.

Venous Murmurs.

The larger veins, more especially the large veins of the neck, are apt to become the seat of murmur of a low pitched humming character. This was first pointed out by Dr. Ogier Ward, and is now generally admitted. Nevertheless, Skoda, Kiwisch, and other observers, have at various times maintained that venous hum originates in the artery-a circumstance which is the more curious, because the fact of its being connected with the veins, admits of easy proof. Thus-1st. The least pressure on the jugular vein, above the point where the stethoscope is applied and the murmur is heard, causes the murmur to cease immediately. 2ndly. The venous murmur, which is a continuous murmur, and the arterial murmur, which is intermittent, sometimes coexist in the same patient, and may be distinctly recognised at the same spot and at the same moment; indeed, in a large proportion of cases, the venous murmur may be heard coincident with the normal sound of arterial pulsation. 3rdly. In some instances, the murmur may be heard along the superior longitudinal sinus, especially towards the torcular Herophili, where there is no artery, and, therefore, cannot be an arterial sound. 4thly. The murmur in the neck is increased in intensity by any cause which accelerates the flow of blood through the jugular veins, and is weakened, or becomes inaudible when the venous current is retarded or arrested. Thus it is increased by an erect posture, and by the act of inspiration, which draws the blood on towards the right side of the heart; it is weakened by a recumbent posture, and lessened or absolutely arrested by any disease which leads to turgidity of the jugular veins with partial arrest of the circulation through them-causes which do not materially influence the production of an arterial sound or murmur.

It must be admitted, then, that the veins are sometimes the seat

of murmur; but that they are not so normally, is evident from the fact that venous murmur does not always exist, and in the majority of persons cannot be heard, except under the influence of pressure by the stethoscope.* It may be desirable, therefore, to investigate the character of this murmur, and the causes from which it originates.

In its character it differs remarkably from an arterial murmur, and therefore, in a diagnostic point of view, is not likely to occasion difficulty. Instead of being intermittent, and of a high pitch, as arterial murmurs usually are, and synchronous with the systole, or with the diastole of the heart, or double, accompanying both of these actions, the venous murmur is always single, continuous, and of a low humming, cooing, or roaring character, somewhat resembling the whispered pronunciation of the word "who." It varies in intensity from one moment to another, and, in certain instances, is not only marked by a regular increase or swell, which is synchronous with the heart's systole, and is probably dependent on the pressure of the contiguous artery, but it rises at irregular intervals, almost to the character of a musical tone.

Sex appears to exert little influence on its occurrence. It is met with in men almost as frequently as in women; and though most common in childhood and the earlier periods of life, it may show itself at all ages, under conditions favourable to its existence. It is most common in the jugulars, especially in the right external jugular, and in the subclavian and innominate veins; but it may be sometimes heard in the superior longitudinal sinus, and is often present in the femoral and other distant veins. Dr. Herbert Davies † and

* Dr. Herbert Davies, who is an advocate for the extreme frequency of venous murmur, is constrained to admit that "the sound will be observed only in certain positions of the neck, and with certain degrees of pressure to be found by repeated trials." (Loc. cit., p. 355.) The necessity, however, for such positions and such pressure is all I contend for. No one would deny the possibility of inducing a murmur by well-regulated pressure, whether in an artery or in a vein, provided only the circulation be sufficiently active; but I would maintain that neither in the one nor in other does a murmur exist without the exercise of pressure, or the existence of some cause calculated to excite an eddy in the blood.

+ Loc. cit., pp. 355-358. Dr. Davies reports venous murmur to have been present in 765 out of 802 children from fourteen months to fifteen years of age, or, in other words, in about 95 per cent.; in 129 out of 150 healthy males between the ages of seventeen and twenty-seven, or, in other words, in about 86 per cent.; in 46 out of 53 healthy females between the ages of sixteen and twenty-eight, or, in other words, in about 86 per cent.; and in 8 out of 67 persons of both sexes between the ages of fifty and ninety, or in about 12 per cent.

Winterich, who have examined a large number of individuals of all ages and both sexes with a special view to this inquiry, report its existence in a vast majority of the population-a conclusion from which I am forced to dissent.

What, then, is the cause of this venous hum? My own investigations lead me to believe, that in most cases it is referable solely to pressure on the veins, whether excited by the stethoscope or by any other means. With a view to a solution of this question, I cut channels of various widths and depths in the extremities of different stethoscopes, so as to fit over veins of different sizes, without exerting any pressure on them. Thus, when the stethoscope was adjusted carefully to the part to be examined, I was enabled to listen to the circulation. in the vein without much risk of producing murmur by pressure—a result which is unattainable by any other method. Proceeding in this manner, I ascertained the absence of venous murmur in 148 out of 196 healthy persons between the ages of fourteen and fifty-nine; or, in other words, I found it present in only 24 per cent., and, probably, in many of these some pressure was exerted, notwithstanding my precautions.

Without attempting to discuss the various theories which have been broached on the subject of venous murmur, I will endeavour to point out the conclusions at which I have arrived after a long series of experimental investigations. Briefly, then, it may be stated, that pressure, whether by the stethoscope or by any other means, will produce venous hum in most cases in which the venous circulation is sufficiently active to excite sonorous vibrations as the result of an eddy in the blood. 2ndly. That venous murmur is seldom met with, unless pressure be exerted on the vein; † but that, in a few instances, it occurs independently of any discoverable pressure. 3rdly. That the rarity of its occurrence without obvious pressure and the frequency of its * See Med.-Chir. Review' for 1852, vol. ix, p. 501. Winterich gives the following as the per-centage of venous murmurs in healthy persons :