Carpenter's principles of human physiology . Mareys Sphygmograph. The production of the pulse is a subject of much interest. The passage of acontinuous current of fluid through an elastic tube takes place in accordancewith the same laws as those which govern its passage through a rigid tube;but if into an already tightly-filled elastic tube which is closed at its extremitya jet of fluid be driven, the first part of the tube undergoes distension, and anoscillatory movement is impressed on the particles of the fluid, which rapidlypropagates itself in the form of a positive wave to the extremity
Carpenter's principles of human physiology . Mareys Sphygmograph. The production of the pulse is a subject of much interest. The passage of acontinuous current of fluid through an elastic tube takes place in accordancewith the same laws as those which govern its passage through a rigid tube;but if into an already tightly-filled elastic tube which is closed at its extremitya jet of fluid be driven, the first part of the tube undergoes distension, and anoscillatory movement is impressed on the particles of the fluid, which rapidlypropagates itself in the form of a positive wave to the extremity of the tube,and is then reflected to and fro along the tube till it dies out. In this casethere is only an oscillation of the particles of the fluid, but no translation of * Op. cit., chap. xiv. MOVEMENT OF THE BLOOD IN THE ARTERIES. 313. them. If, however, the extremity of the tube be open, and a jet or successionof jets of fluid be forced into it whilst -gm 135> the fluid it contains is in motion, theresult is a combination of undulatorymovement with current movement. Thevelocity of the wave is proportional to theelasticity of the tube ; it varies inverselywith the density of the liquid; it dimi-nishes gradually with the length of thetube, and it increases with the rapidityof impulsion of the fluid.* The amplitudeof the wave is proportional to the quan-tity of fluid which penetrates into thetube and the briskness of the jet. Itdiminishes as the wave Thefluctuations of the Pulse in the livingbody without exposure of the artery canbe rendered apparent by the use of aninstrument originally invented by Vier-ordt, but materially modified and im-proved by Marey, termed the Sphygmo-graph. The general arrangement of theinstrument is shown in Fig. 134, wherethe part B B is applied to the forearm,whilst the press
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectphysiology, bookyear1
