Volume 3

A system of practical medicine : comprised in a series of original dissertations / arranged and edited by Alexander Tweedie.

  • Tweedie, Alexander, 1794-1884.
Date:
1840
Catalogue details

Licence: Public Domain Mark

Credit: A system of practical medicine : comprised in a series of original dissertations / arranged and edited by Alexander Tweedie. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    noticed by Andral, Louis, and Dr. Cowatj, who ascribe their discovery to the late Dr. Jackson, a young American who studied at Paris. They deserve at- tention, and are obviously dependent on the causes which have been men- tioned. It is needless, however, to distinguish them in general descriptions, and we shall class them together as the sounds of respiration. The sounds of respiration can be heard on applying 'the ear to different parts of the chest, being transmitted through the parietes to the parts beneath with sufficient distinctness ; and as the healthy sounds vary in these different parts, we may judge of the natural distribution of the tubes, by listening to these sounds. Thus we find in any part of the neck, and at the upper part of the sternum, there is the hollow blowing sound which results from the passage of air to and fro in the trachea, which is therefore called tracheal respiration. A little lower down than this, over the space of two or three inches on each side of the top of the sternum, between the scapulaj, and sometimes in the axillcC, there is the sound called bronchial respiration, its whiffing or tubular character denoting that it is produced by the passage of air in the bronchial tubes. In most other parts of the chest is heard the vesicular respiration, which is a diffused murmur caused by the air penetrating through the minutest tubes, and into their numerous vesicles or cells. The question naturally occurs, why is the bronchial respiration heard m comparatively few parts of the chest, when bronchial tubes of considerable size are distributed in so many parts of the lungs, within an inch or less of the surface ? Why is not the sound a mixture of the tubular and vesicular sounds ? The answer and explanation is, that in consequence of its softness and in- equality of density, the healthy tissue of the lung is a bad conductor of sound, and does not transmit the sound of bronchial respiration to the surface, except in points Avhere the tubes are large, and approach quite close to the walls of the chest. The flaccid tissue, composed of the different materials, membrane and air, effectually arrests all the slighter sounds produced in the tubes within it. An important corollary from this is, that, as this arrest of the sounds of the interior depends on the light spongy structure of the lung, so any disease, in- creasing the density of that structure, augments its conducting power, and en- ables it to transmit the sounds. Hence we find that a great increment of solid or liquid in the lung, as in pneumonia or tuberculous disease, or tbe compres- sion of its superficial parts by a moderate quantity of liquid in the pleura, as in a recent pleurisy, often not only diminishes the vesicular murmur in con- sequence of the obstructed state of the cells, but also adds a bronchial or tubular sound of breathing in those parts where naturally the respiration is purely vesicular, . , ^ As the several sounds of respiration depend on the resisted motion ot tne air, so they vary according to the velocity of that motion, and the degree and nature of the resistance to it ; they are loud when the air passes in and out forcibly and quickly, and low when it passes gently and slowly. So, on lis- tening to a person’s breathing, it may be scarcely audible at its ordinary rate ; but if he breathe quick and short, it will be distinct enough. Taking a long breath may not answer the same purpose; for although much air is thus taken in, it may not enter with sufficient rapidity to cause the increased sound. Touching answers better, for the full inspiration which succeeds coughing is Kene°rally quick also ; and it is often useful, where the sounds are obscure, to mao'nify them by this more forcible act. But there is a limit to this power of increasing the sound of respiration by increased effort. If an individual tries to breathe very hard and quick, as after violent exertion, the movements of the lungs cannot keep pace with those of the external muscles of respiration, and the air does not freely enter, the sound will be diminished or altered rather than increased. , . As we can vary the sound of respiration by varying the act in the same in- di vidual so we find that a difference exists naturally in different individuals; in some as in many robust adults, the ordinary respiratory sound is very low