As a general rule, blood-sounds are characterized by great softness : and a whizzing, grating, or musical noise may be safely concluded to depend on some valvular defect.
Local distinctness is one of the beat distinguishing features of mites! insuf ficiency. It is to be traced when no hypertrophy of the organ is present, and very commonly coincides with a history of rheumatic fever. Irregular action, kebleness of pulse, congestion of the lungs, &c., leave no doubt as to the regurgitation of the blood through the mitral orifice when the position of the murmur is doubtful, and may even be sufficient to prove this condition when no murmur can be heard at all. It is not necessary to go into the further question whether the imperfect closure of the valve depend upon alteration in its own texture preventing the edges from accurately adapting themselves to each other, or upon changes in relation betireen the size of the cavity and aperture, and of the membranous valve, or of the length of the corche ten &nese ; though each of these causes may give rise to nntral insufficiency.
An memo murmur is very seldom to be traced in greater intensity towanis the apex, but that it is so occasionally is quite certain ; and the fact must not be forgotten. The general indications which would confirm the opinion that it was due to blood-change only, are that the patient is young, and has never had rheumatic fever, and that the aspect is decidedly antemic--blood passing backwards through the mitral valve tends to produce blueness of skin, from obstruction to the circulation in the lungs : a bruit in the carotid artery or in the jugular vein, when none can be traced at the base of the heart, is also a valuable indication : the pulse in such circumstances is not at all deficient in power, but it may not be perceptibly so, even with decided mitre insufficiency, when regurgitation takes places only to a small extent. It may be suggestea, in explanation of this form of blood-murmur, that the vibration is excited by the friction of the particles against the columns: came when the blood is in such a condition that it can be readily produced, and that it is heard with greater intensity towards the apex only because the base of the heart and the great vessels were deeply covered by lung-tissue, and the apex compara tively exposed in the particular instances in which it has been noticed ; and this is the more probable, because it very generally varies in position and intensity from day to day.
Tricuspid regurgitation seems to be a very common condition, and is very rarely indicated by the presence of a bruit. This is to be explained no doubt by the minor force of the right ventricle; and it is therefore only in conditions of very decided disease that a tricuspid systolic murmur is met with: such cases, pathologists know to be very much rarer than corresponding disease of the mitral valve.
At the base of the heart bruits are so often dependent on blood-changes, that the diagnosis can rarely be made with any approach to certainty from the character and position of the murmur itself: and we therefore look in the first instance to the aspect of the patient, the history of the case, and the evidence of disease of the heart from diastolic murmur or hypertrophy, to aid in the determination. In no case perhaps is error more liable to be committed than in mistaking nervous excitement for hypertrophy, and deciding that there fore the bruit heard is an indication of valvular disease.
In speaking of chronic blood-ailments (Chap. VIII., I 4) those circum stances were mentioned in detail in which an anemic bruit is probably to he heard ; and it was there stated that, as the cause of the production of sound is in the blood itself, the motion among its particles caused by its passage through the healthy heart is sufficient to excite the vibration, and that the point at which the bruit is heard in its greatest intensity is only that which is most superficial ; but that, as a general rule, it tends to be diffuse, and is audible over a large surface. In the majority of cases, a systolic murmur at the base heard relatively louder over the second interspace on the right side of the sternum, indicates disease of the aortic valves, while one relatively louder in the same interspace on the left side, directly over the base of the heart, or, extending towards the left shoulder, is only a blood-sound : a local bruit in the third interspace on the left side, which is not propagated in either direction, is most commonly caused by valvular disease.