Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee.

  • Gamgee Arthur, 1841-1909.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee. 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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    of the frog's leg follows each systole of the heart. As this result occurs constantly (pi-oviding the tissues of the frog be sufficiently irritable), i.e. as tetanic contraction is never induced, this proof afforded by the so-called rheoscopic frog is believed to be conclu- sive. There is a difficulty in the way of admitting the contraction of the heart to be ' simple,' which must, however, be stated. A muscle when performing a simple muscular contraction does not emit a distinct note, the muscular noise being produced by a suc- cession of contractions following one another about twenty times per second. How then does the heart muscle emit a note during contraction ? The question yet remains unanswered.] The second, diastolic, sound follows immediately, and therefore occurs at the commencement of the ventricular diastole. It is shorter and clearer than the first sound, and is caused by the sudden closure of the aortic and pulmonary semi-lunar valves, the compe- tence of which is necessary to its production (Williams The cardiac impulse may be made to register directly the movements of the heart. For this purpose an air-tight drum is placed against the chest wall, and the vibrations of the air con- tained in it are propagated by a suitable arrangement to a writing lever, which registers them upon a travelling band of paper (' Car- diograph ' of Marey). The arterial pulse serves for the indirect registration of the heart's action (see Kymograph, Sphygmograph). \_The Cardiograph.—The principle upon which the cardiograph is constructed will be understood by referring to fig. 3, which represents one modification of the original cardiograph of Marey. A is the cardiograph proper; it is a very shallow metallic cup, over the upper part of which a sheet of caoutchouc has been stretched and then fastened air-tight. The cup A has attached to it a short metallic tube, over which a narrow elastic tube can easily be slipped so as to connect it with the apparatus B. To the centre of the caoutchouc surface a is fixed a light metallic disk h. o- is a bent spring, into which fits a screw bearing the ivory or vulcanite knob d. By altering the screw, one end of it can be made exactly to touch the metallic disk b ; any pressui'e applied to the knob d will then cause a depression of the elastic membrane a. B may be termed the recording tambour. It is a metallic cup, over the upper surface of which caoutchouc is stretched, and which, like the cardiograph, has a metallic tube leading from it, by means of which it can be connected with the cardiograph. To the elastic upper surface of the tambour is fixed a metallic disk, the centre of which bears the fulcrum of the light wooden lever c, which carries at its free extremity a light metallic or quill point. The cardiograph and the tambour being connected, it is obvious ' Williams, Pathnhgy and Diagnosis of the Diseases of the Chest, 4th edit., 1840 ; Report of the British Asuociation, 1837.