The blood on its return from the veins next presents exactly similar relations to the tricuspid valve on entering the right ventricle and the pulmonic valves as it leaves it ; but bruits are very seldom developed on this side of the heart, except when caused by blood-change ; and then they are heard much more loudly in tbe pulmonary artery than elsewhere, because at the second inter space is found the most superficial portion of the circuit. We know that tricuspid regurgitation often takes place, for we see the pulsation of the jugulars corresponding in time to the systole and apex-beat, but it occurs without bruit ; and though this result be no doubt partly due to the more feeble contractions of the right side, it also depends, in all probability, on the construction of the valve being such as to permit this regurgitation for the relief of the circulation : bruits at the pulmonic valves, independent of blood.. change, are necessarily rare, from the comparative infrequency of disease at the root of the pulmonary artery.
We have learnt, then, that a diastolic murmur from the apex towards the centre of the heart, indicates very decided mitral disease ; one from the base towards the centre, imperfect closure of the aortic valves. We have learnt, too, that a systolic murmur, of local character and distinctness towards the apex, may be pre sumed to be dependent on disease of the mitral valve in the majority of instances, and that a murmur heard between the third and fourth cartilages on the left, traceable over the sternum to the interspace between the second and third cartilages on the right side of the chest, may probably be dependent on disease about the root of the aorta, or the aortic valves ; and the more defined and distinct it is, the more likely is this conclusion to be true ; the more diffuse and indistinct, the more care must be taken before coming to any judgment on the subject.
For the purposes of diagnosis, the sound is only one element in the investigation, which has to be compared with all the others, and has to be reconciled with them on rational principles, not by forced and overstrained hypotheses. The points to be considered are a. The pulse. (1) It is essentially weak, often irregular, and sometimes almost imperceptible in mitral insufficiency. (2) It is jerky, thrilling, and hammering in aortic insufficiency. (3) It is weak in cases of diastolic murmur produced at the mitral valve, because such a condition is necessarily connected with mitral insufficiency. (4) If it have at all a thrilling character, while also firm and resisting, in cases of systolic murmur at the base, the probability of aortic disease is much increased.
b. The existence of hypertrophy renders the diagnosis of val vular lesion more certain. But we sometimes find that dilatation,
without corresponding increase in size of the valve-flaps, renders them inadequate to close the aperture. When regurgitation, therefore, occurs, it is more correct to speak of insufficiency than lesion of the valve, although practically that insufficiency depends in by far the larger number of instances on actual dis ease of the valve-structure, and is the result of the lesion, whether that have originated suddenly in rupture, more slowly in the changes consequent on inflammation, or still more slowly in chronic degeneration.
Shortening of the chords tendinese sometimes seems to produce an insuffi ciency of the mitral valve, which may last only for a short time. This expla nation has been offered of the mitral murmur of chorea, when it has disap peared as the spasmodic muscular movements have ceased. I have observed a similar effect follow on rheumatic pericarditis. An intense mitral murmur with evident regurgitation was heard, when the friction sound had ceased for some weeks, while the patient continued under observation; but at the end of three or four months, during which no treatment was pursued, it had entirely disappeared : the heart's sounds were then found perfectly normal, and only a suspicion of an adherent pericardium could be entertained.
c. The general aspect and history of the patient serve to indi cate the probability of heart disease on the one hand by capillary congestion, or of blood changes on the other, by an appearance of anaemia. The indications from the venous circulation are also not less valuable than the capillary—jugular pulsation as caused by the blood being thrown back at each systole into the veins— venous hum as proving the existence of blood-change.
When the systolic murmur is heard towards the apex, a weak pulse con firms the diagnosis of mitral disease; a well-filled pulse, though perhaps a very soft one, must lead to grave doubt as to whether the sound depend on mitral insufficiency; and if the bruit be diffuse, and the aspect anemic, the rational explanation would seem to be that it is heard there only because of some accidental relation between the chest and the organs of circulation, by which the sound of vibration of blood is conveyed to the ear better from the interior of one of the ventricles than from either of the great vessels. Again, if there be no anaemia, but, on the contrary, venous and capillary congestion, with jugular pulsation, indicating that the blood is thrown back from the right side of the heart, a full pulse might lead us to suspect that the sound was not improbably due to disease of the tricuspid valve.