B. Systolic Murmurs.—The first question for consideration with regard to a murmur of this class is whether it be formed at the apex or at the base of the heart; and this is to be determined by the relation of its point of greatest intensity to the outline of the organ given by percussion, and the position of the apex-beat. A very moderate degree of care in making the examination is gene rally sufficient to determine this point, which can only be rendered doubtful when there is no special locality where the intensity is greater than elsewhere.
1. Systolic Murmurs at the at the centre of the heart, we listen to the quality and rhythm of the sounds heard there, and move the stethoscope gradually downwards and outwards : the lst sound will have lost its distinctness, and will present a character of roughness at the centre, which becomes a decided bruit at the apex.
a. When the bruit is dependent on imperfect closure of a valve, the ear generally detects a spot of limited dimensions at which the murmur is much more distinct than elsewhere—the rough ness of the 1st sound passes suddenly into loud bruit.
b. This point of greatest intensity varies somewhat from un known causes. In insufficiency of the mitral valve, it is to be found most commonly on a level with the apex, about an inch nearer to the sternum ; and next in frequency, about an inch above the apex-beat, near to the nipple ; less commonly some where between those points.
e. When the murmur is heard in greatest intensity consider ably to the right of the apex-beat, or at the end of the ensiform cartilage, we may suspect that it is due to imperfection of the tricuspid valve ; but this sound is less local, and therefore less certain.
d If the murmur, though decidedly more distinct towards the apex than at the centre of the heart, present no local point of greatest intensity, we may still conclude that it is a valvular sound if the heart be increased in size, and, in all probability, a mitral murmur.
e. Occasionally, mere changes in the quality of the blood pro duce a murmur which is audible over the centre of the heart, but seems to become more distinct towards the apex. It is therefore necessary, in such cases, to study the history and symptoms with care, in order that our diagnosis may not be at variance with some particular indication which has been overlooked.
2. Systolic Murmurs at the Base.—Proceeding in the same man ner from the centre of the heart, the murmur becomes louder and more distinct as we travel upwards ; but the ear seldom comes upon a point where its intensity is so suddenly increased as at the apex. Here it is that bruits dependent solely on blood-changes
are most commonly found ; and it is sometimes a matter of great difficulty to determine whether there be any structural alteration or not.
a. When a diastolic bruit is also heard, there is necessarily valvular disease, and, as we have already mentioned, probably disease of the sortie valves.
b. If there be evidence of enlargement of the heart, the bruit is also almost certainly dependent on disease of the aortic valves, or root of the aorta. It must, however, be clearly made out that it is real hypertrophy and not mere nervous excitement.
c. A murmur which c,an be distinctly localized at the base of the heart, and is only faintly audible, or cannot be heard at all above the third rib, is probably due t,o disease of the valves ; one which is diffuse and cannot be readily localized within the limits of the prtecordial dulness, is more likely to be caused by altered blood.
d. A murmur which can be traced from below the third car tilage on the left side to the second interspace on the right, is generated in the aorta; one heard most distinctly in the second interspace on the lett side, is probably produced in the pulmonary artery.. .In the one c,ase there may be disease of the valve, in the other there is probably only change in the character of the blood.
e. When there is any suspicion of disease, the history and general symptoms must be carefully inquired into : an alumni° state may account for the existence of a murmur, and, under all circumst,ances, necessarily increases its intensity.
Some authors distinguish pre-systolic ind post-systolic murmurs from such as may more properly be called systolic. The names are ill chosen, and apt to convey a wrong impression, and the division is too minute to be followed by the student ; but the possibility of some variation in the time of their commencement should be remembered, Bo as not to confound a systolic mur mur, which does not exactly coincide with the apex-beat, with a diastolic one. The one ends at or near to the time of the beat, the other begin8 then, and ends long before the heart can be again felt impinging on the ribs.