RESPIRATORY SOUNDS are of the greatest importance in the diagnosis of the dis eases of the lungs. They may be divided into (1) those directly resulting from inspiration and expiration. and (2) those of the voice, including coughing.
In time healthy state of the lungs, two distinct sounds are heard, on applyinn'the ear, either directly or through the intervention of the stethoscope, to the walls of the chest— one called the vesicular sound, because it is supposed to be caused by the passage of the air from the ultimate tubes into the air-cells or vesicles; and the other the bronchial sound, because it is generated in the bronchial tubes by the air moving through them.
• The vesicular sound, known also as the respiratory murmur, is mainly produced during inspiration, being very faint, and sometimes scarcely perceptible during expira tion. It is rather a rustle, than a murmur, and has been compared to the sighing of a gentle breeze among leaves, to the sound made in the deep inspiration of a sleeping per son, etc.; but a single minute's application of the ear to the chest of a healthy person below the collar-bone, will give a clearer idea of its true nature than any mere description could convey. The sound is inure distinct in thin than in fat persons, in women than in men, and in children than in adults. Indeed, it is so loud in children, that when an unusually noisy sound is heard in an adult, it is said to be puerile. The bronchial sound has a blowing character, such as maybe producer) by blowing air quickly through a tube, and is altogether distinct from the former. It may be most clearly heard over the trachea or windpipe, and at the upper part of the sternum or breast-bone.
Such are the sounds as they occur in the healthy lungs. In disease, any change which tends to impair the respiratory function in one part of the lungs, will make the vesicular murmur abnormally weak there, and abnormally loud in the remainder; and there are other changes, besides a mere increase or decrease of intensity, that sometimes occur, and into which we have no space to enter. The bronchial sound is also liable to
morbid alteration; for example, it may be heard in parts of the chest where it is usually inaudible,iu consequence of condensation of the surrounding pulmonary tissue, or from di latation of the tubes. independently of condensation; and in violent dysprura, it may some times be heard over,the whole chest without any change of structure. These morbid sounds are only modifications of those which occur in health. There Eire, however, other sounds generated by disease which are highly important in diagnosis. These are termed idles by the French, and rattles, sibitus, rhonchus, etc., by those English writers who do not adopt the French term. They may be briefly divi.led into the dry and the moist Hiles, the former being caused by the passage of the air, with increased rapidity, through nar rowed portions of the bronchial tubes; while the latter arc formed by the passage of air through a fluid of more or less tenacity in the bronchial tubes, causing the formation of a succession of bubbles, whose bursting occasions the sound.
There are two other morbid sounds- connected with the respiratory system which deserve to be named in this list, viz., metallic Molding and the friction sound. Metallic tinkling is a quick and sharp sound, resembling that produced by striking a glass vesssel with a pin. Its occurrence affords evidence of the existence of a cavity of considerable size, containing air, and surrounded by firm walls; but how the sound is produced is not definitely settled. The friction sound is produced by the rubbing together of the pulmonary and costal pleura when rough from inflammatory action, and is indicative of pleurisy.