Sphyg′mo-graph.
An instrument applied to the pulse to ascertain and record the quickness of its beating, and its uniformity or irregularity, as the case may be; also, the degree of force with which the blood is driven through the arteries, — or, in other words, the contractile power of the heart. Of late years this apparatus has been used by physicians for purposes of diagnosis and in various physiological investigations. It was originally devised by Vierordt, and subsequently greatly improved by Marey. Marey's instrument, as originally constructed, consists of a long frame a b, to which is attached a strong steel spring c, about four inches long, and having at its free end a pad d, which presses upon the artery; an arm e, having a knife-edged projection f at its free end, is attached to the spring c, and carries the regulating screw g, which governs the amount of vibration of the recording lever h i, also provided with a compressing spring k; this lever is of the third kind, is very light, and carries a thin steel pen or scratcher at its tip. A screw l determines the amount of pressure of the pulse-spring A recording paper is fixed on a flat metal backing, connected with clock-work mechanism, which runs for about 10 seconds; the whole being attached to the frame a b. The instrument is bound on to the arm by a silken cord attached to pegs at its sides. The knife-edged projection f taps the lever h i at each pulsation with a force proportionate to the strength of the pulse; the lever describes an irregular curve on the paper, indicating the number and strength of the pulsations, and the momentary variations in their force. |
| Sphygmograph. |
