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as we have already seen, of roughness or deposit on the inner surface of the vessel. It would appear, indeed, from the labours of Chauveau and Marey, that roughness of the internal surface of arteries does not anywhere, nor in any case, give rise to murmur. But the question is still open for discussion, whether the condition of the blood produces this modification. Agreeing with the opinion that arterial murmur is due to contraction of the artery at the point of murmur, and to the vibration incidental to a change in the arterial tension, I cannot but state that in many cases where I have met with intense murmur, there have been signs of anæmia; and that the murmur has borne a relationship in intensity with the more determinate indications of the anæmic condition. There are various methods of explaining this observation, the best of which is that of Marey; viz., that in anæmia there is a feebler arterial tension and less resistance to the current of blood in the capillaries. But whatever the explanation, it is certain that the relationships I have pointed out are true; and that anæmia, though not a cause of the murmur, has a qualifying influence
EXACT CHARACTER OF SUBCLAVIAN MURMUR.
The murmur differs in character in different cases, and sonetimes in the same case. It may be a soft musical coo, so short and so slight as to be mixed with and obscured by the respiratory sounds. It may be a loud, coarse, almost snorting gush, conveying an unpleasant thrill to the ear, and, during its transit, obscuring the vesicular murmur of respiration. It may be loud, and yet so short, as to resemble a sound produced by a quick blow, with dull resonance. These are the three typical forms of the murmur, but between them there may be various distinctive shades. The musical cooing murmur, for example, may be intensified to a whistle, or a ringing noise; and the coarse murmur, to an absolute rasp. The murmur under one or other type is always best developed when it occurs in the right subclavian space, but it is most common on the left side.
DIAGNOSIS OF SUBCLAVIAN
Differential Diagnosis. There are four physical signs of disease, diagnosable by the stethoscope, with which subclavian murmur may possibly be confounded, and especially by those who are not familiar with the details, as well as the principles, of physical diagnosis. These physical signs are
Aneurism of the aorta at the arch, or of the innominate artery, or of the subclavian itself, are the first diseases to be differentiated. I have said, that on four occasions I have known subclavian murmur set down as aneurismal; I may add to this, that in one of these cases the life of the patient was refused for insurance on the suspicion of subclavian aneurism. The following diagnostic points are, however, always sufficient to establish the difference between subclavian murmur and any thoracic aneurism.
In aneurism the character of the bruit is usually the same at all times, the point of maximum intensity being one fixed spot, on which the mouth of the stethoscope may be placed, day by day, with the same effect. In subclavian murmur, the bruit may change in character several times during one examination ; being at one time coarse and loud, at another gentle and musical. The point of maximum intensity may also differ by the variation of an inch laterally on either side.
In aneurism the murmur is permanent. In subclavian murmur the sound comes and goes. It will sometimes stop in an instant, and not reappear for many hours. In one case I knew it to be absent for three weeks, and then suddenly to recur and remain for a period equally long; again to subside, and again to present itself; and so on during many months of observation.
In aneurism, the murmur is not influenced by the movements of respiration. In subclavian murmur, the sound can be intensified by a moderately full inspiration; can often be stopped by a forced inspiration; and, again, can be equally stopped by a prolonged expiration.
In aneurism, the stethoscope produces no change in the murmur, however firmly the pressure may be applied ; except in extreme cases, where the tumour protrudes through the thoracic wall. In subclavian murmur, the firm application of the stethoscope will itself check the exhibition of the phenomenon.
In aneurism, movements of the arm do not influence the sound. In subclavian murmur, the sound can invariably be modified by merely raising the arm, and changing the angle of the limb to the body.
In aneurism, there will commonly be present dulness on percussion over the seat of the pulsation; such dulness being independent of tubercular disease of the lungs. In subclavian murmur, if in the region of the murmur there is any dulness on percussion, the stethoscopic and other physical signs will, in the majority of cases, perhaps in all, show that the deficient resonance is due to tubercular deposition.
In aneurism approaching the surface there may be fremitus; but the fremitus is permanent under all conditions. In subclavian murmur there may be fremitus; but this can be made to disappear by movement of the arm on the side affected, and also by a deep expiration, or a very deep and sustained inspiration.
In aneurism of any of the three great vessels I have named, there will be, as a general rule, symptoms of dyspnæa and respiratory oppression. Subclavian murmur is not, per se, accompanied with any such complication.
Finally, as a diagnostic difference between subclavian murmur and subclavian aneurismal murmur, this may be observed; that, if simple subclavian murmur be present on one side, it can usually be detected on the other side; and when the two sounds
are traced downwards, towards the sternum, they are found to be lost, showing that they have no common point of origin, but an origin purely local in each artery. Now, whilst double subclavian aneurism is not an impossible, it is an unrecorded phenomenon, and in common experience is so rare, that the fact of double murmur may be considered as affording direct evidence against aneurism as the cause of the abnormal sounds.
The diagnosis as between subclavian murmur and cardiac murmur is comparatively easy. By carrying the stethoscope from the subclavian region to the cardiac region, it will be detected in pure cases of subclavian murmur, that the heart-sounds are both distinct, and that the bruit in the upper part of the chest is entirely unheard at the heart. However loud it may be in its own region, subclavian murmur never intrudes itself on the cardiac music. This line of diagnosis is therefore direct. But there are cases, and I have seen two such, where, together with subclavian murmur, there was systolic cardiac murmur from mitral disease. But here again I had no difficulty in distinguishing the two morbid sounds; for the mitral murmur was permanent, while the subclavian murmur was intermittent; the mitral murmur was prolonged, while the subclavian was short and sharp; and lastly, on carrying the stethoscope from the subclavian space downwards, towards the heart, an intermediate point was found, where the subclavian murmur was lost and the cardiac murmur began to be