On the sounds of respiration and of the voice / [Peyton Blakiston].

  • Peyton Blakiston
Date:
[1839]
Catalogue details

Licence: Public Domain Mark

Credit: On the sounds of respiration and of the voice / [Peyton Blakiston]. Source: Wellcome Collection.

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    tion which is heard in such cases. It must be remembered, however, that the current of air in the bronchial tubes owes its existence to the expansion of their vesicular extremities, and that when their expansibility has been de¬ stroyed by the deposition of solid matter in them, that moment the current must cease in these tubes, and with it the sound of respiration within them. Were the larger tubes sufficiently elastic to keep up a current, then, in a solidifica¬ tion of a whole lung, we should hear loud bronchial respiration, which is not found to be the case. Dr. Jackson, of New York, was the first to notice prolonged expiration as a characteristic sign of bronchial respira¬ tion. He writes*, “ In some commenc¬ ing cases of phthisis, where the respira¬ tion is not yet truly bronchial under the clavicle, when we still hear the vesicular expansion and nought else on inspiration, I have discovered the bronchial sound on expiratiou. In other words, as the tubercular deposit advances, the bron¬ chial expiration may be heard before the bronchial inspiration', it may be heard at an earlier period of the disease, and may thus become a very important sign, as making known the disease yet sooner after its origin. This circum¬ stance is very explicable. As soon as tubercular matter is deposited, there exists a solid material around the bronchia, which will transmit the sound made by the passage of the air through these tubes; but thus early a great portion of the lung, even in the part affected (the summit), is permeable to the air, and therefore the murmur of vesicular expansion on inspiration en¬ tirely masks the sound of the air passing through the bronchia, which would otherwise have been transmitted through the surrounding denser medium. On expiration, however, circumstances have changed: the air, on passing through the bronchia, produces the same sound as on its entrance, and as now there is no vesicular expansion to mask it, it is easily transmitted through the diseased or condensed part to the ear of the observer.” Fully acknowledging the practical value of the prolonged sound of expiration as a diagnostic sign, I cannot admit the correctness of Dr. Jackson’s observation that it is heard at a period w hen the sound of inspiration is purely vesicular. Although it is easier to discover the presence of a sound at a time when none was previously heard, than to detect an alteration in the quality of one previously existing, yet whenever I have perceived the sound of expiration prolonged at the surface of the chest, I have at the same time found the sound of inspiration stronger and coarser than usual; in short, I have found both sounds bronchial. Neither do I think can Dr. Jackson’s explana¬ tion be considered satisfactory. We cannot understand how the strong coarse sound of bronchial respiration can be masked by the softer and weaker sound of vesicular inspiration, which has in fact been shewn principally to consist of that bronchial respiration modified and w eakened by divergence, and borne up to the ear by the current of air. Again, were any portion of lung to be solidified and made sufficiently homogeneous to transmit the sound of expiration, it would also transmit the coarse un¬ diverged sound of inspiration which takes place in the same tubes. I would submit that when bronchial respiration is heard over a solidified portion of lung, it is caused by the assing and repassing of the air through ronchial tubes leading to healthy expansible vesicles, and it is made sen¬ sible to the auscultator by his ear being brought into mediate contact with their sides by the solid lung. Voice.—I shall next endeavour to discover the causes which tend to modify the sounds of the voice. According to the researches and ex¬ periments of Professor Willis, the voice is formed in the larynx by the vibration of the vocal cords or plates when their planes are in a vertical position, being put into motion by the passage of the air from the lungs. The vocal apparatus, therefore, is a wind-instrument, consist¬ ing of a tube with membranous tongues. It has long been noticed that timbre, a quality of tone of wind-instruments, depends much upon the material of which they are made. Wishing to know more upon this subject, I successively placed similarly constructed pipes of wood and of metal on the wind-chest of an organ; and I found that the tone became coarse, and buzzing, in propor¬ tion to the elasticity of the material. Having next varied the weight on the bellows, I found the coarseness of tone * Life of Dr. Jackson, p. 129.
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