A medical handbook : for the use of practitioners and students / by R.S. Aitchison.

  • Aitchison, R. S. (Robert Swan)
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: A medical handbook : for the use of practitioners and students / by R.S. Aitchison. Source: Wellcome Collection.

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    percussion-tone as resulting certainly from the resonance of a great number of unequal chambers, but still striking the ear as a single sound, I and all that is available for the comparison of the healthy with the con¬ solidated lungs. The variations in the intensity and pitch in relation to this single percussion-sound would then be in harmony with the law already stated concerning resonant chambers, viz. :—that the smaller the air space the weaker is the intensity and the higher the pitch. If, on the other hand, we attempt to regard the percussion-sound as 1 a combination of sounds produced by distinct and separate resonance chambers all varying in size, and each having its own intensity and pitch, it is possible to conceive that the removal (by consolidation) of a number of the smaller and high-pitched elements (vesicles), while it diminishes the intensity of the percussion-tone as a whole, might not raise the pitch, as the larger elements (bronchi), if between the plexi- meter and the consolidation, would tend to keep the pitch low. As this can only apply to small consolidations—the larger ones diminishing the air spaces to such an extent as to diminish the intensity and raise the pitch, as a whole—Guttman's dictum may be accepted for practical purposes. Although the membranes and resonant spaces are indissolubly associated in the production of percussion-sounds, they are here considered separately, in order to make clear the part each plays in the alterations of the intensity and pitch of the sounds I. The Membranes.—A. The thoracic parietes; B. The lung. A. The thoracic parietes affect the intensity and pitch by the state of their tension and density. Increase of muscle on one side (labourers), deposit of fat, oedema, rigid and curved ribs, local thickening externally, or internally (pleura), and deep inspiration, will all diminish the intensity and raise the pitch, because the vibra¬ tions of the chest-wall are diminished in amplitude, and quicker in f time. In these cases the percussion requires to be more forcible to bring out the resonant-tone, light percussion giving only a dull or Hat note unless the air spaces beneath are caused to vibrate. On the other hand, the intensity is increased and the pitch lowered by muscular atrophy, emaciation, &c. B. The lung, which may be regarded as the much thickened and altered internal layer of vibrating membrane, plays an important pari in the production of the percussion-tone, as the state of tension of this organ is subject to variations which may affect the intensity and pitch. The lung in its normal state is slightly over-distended, and it has its peripheral surface to a great extent applied accurately to the external layers (thoracic parietes), and by virtue of its own elasticity it has a marked tendency to collapse. Should this occur from any pathological cause (as in early pleuritic effusion), the per¬ cussion-tone over it would become more intense and lower pitched because the lung-tissue has become more flexible. Should the collapse, however, become more complete, the lung then becomes more compact, ceases to yield flexible vibrations, and may now be regarded as a condensed body separated from the external layers of vibrating membrane by some pathological product, which may itself I