On the action of the muscular coat of the bronchial tubes in respiration / by C. Radclyffe Hall.

Date:
1850
Catalogue details

Licence: Public Domain Mark

Credit: On the action of the muscular coat of the bronchial tubes in respiration / by C. Radclyffe Hall. Source: Wellcome Collection.

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

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    development of the bronchial muscular coat in the smaller tubes; but if elasticity be the agent, this correspondence is wanting; elastic tissues exist in largest proportion in the larger tubes. In the larger tubes we find plates of cartilage, and longitudinal elastic fibres thickly and closely packed. Between these, and separating them, is placed a thin layer of unstriped muscular fibres, which, as they are not firmly attached to the plates of cartilage, can have but little influence over them; and next to the longitudinal fibres, the mucous membrane. In the smaller tubes the cartilages no longer exist; the longitudinal elastic fibres are all placed lengthwise, never across the tube; they branch at their extremities, and intertwine to an extent sufficient to ensure their keeping together, but not sufficient to enable them to either lessen or enlarge the tube in the wall of which they are situated. The circular muscular fibres form a thicker and stronger layer than in the large tubes, external to and surrounding the longitudinal elastic bands. Arrived at the com- mencement of a vestibular passage, or passage of entrance to several air-cells, the muscular coat ceases abruptly, whilst the longitudinal elastic fibres spread out from under it, and stretching in curved loops over each bunch of air-cells, form the frame-work upon which the thin basement membrane, with its delicate pavement epithelium, is spread to constitute the wall of an air-cell. It results from this arrangement that the openings of the air-cells can never become closed by any action of the muscular coat. Had the muscular fibres been the most internal, their energetic contraction might have closed up (like a sphincter) the door of the vestibule, and instead of dyspnoea, a fit of asthma would have caused asphyxia. As it is, the effect of the contraction of the circular muscular fibres is to press upon the longitudinal elastic bauds; these, being always on the stretch, by opposing the pressure, render it uniform and equal throughout the tube; and by their expanding to embrace the air- cells at the point where the termination of the muscular coat leaves a ring of muscle with a free margin, convey the muscular com- pression on to the walls of the cells, and effectually prevent any ring-like constriction. Thus the channel of the tubes is kept smooth and free, and the openings into the air-cells patent, under every degree of expansion and contraction of the lung.* * Did space permit, it would be easy to show the hearing which these considerations have on the mechanism of the production of emphysema.