A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . r is obser\edin the systemic arteries. MTien they are both quickand strong, only the primary effects appear, and theaortic pressure falls in inspiration and rises in expira-tion. The typical result is seen only in ordinarybreathing when the rate is slow enough to permit 142 REFERENCK HANDBOOK OF THE MEDICAL SCIENCES Blood, Circulation of both the primary and secondary changes to producetheir proper effect (see Fig. 725). In this case thepressure first falls during
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . r is obser\edin the systemic arteries. MTien they are both quickand strong, only the primary effects appear, and theaortic pressure falls in inspiration and rises in expira-tion. The typical result is seen only in ordinarybreathing when the rate is slow enough to permit 142 REFERENCK HANDBOOK OF THE MEDICAL SCIENCES Blood, Circulation of both the primary and secondary changes to producetheir proper effect (see Fig. 725). In this case thepressure first falls during iiisi)iration to a minimum(primary effect) and then rises again (secondaryeffect); in the succeeding expiration the rise continuesfor a short time to the maximum (primary effect) andthen the pressure falls again (secondary effect).The main effect of inspiration, therefore, is to pressure and the main effect of expiration tolower it. The curve frequently shows also changesin the rate of the heart which beats slower duringexpiration and faster in inspiration. These heart-rate changes are brought about through nervous. Fia. 725.—Carotid Blood-pressure Tracing of Dog. Vagi uotdivided. J, Inspiration; E, expiration. (Stirling.) influences that be considered later, and it needonly be stated in this connection that they are notof sufficient moment to affect the general course ofthe phenomena here described. The Mechanics op the Heart.—The circulationof the blood throxigh the vessels is maintained bythe energy of the beating heart. Before consideringthe causation and regulation of the beat, it will beconvenient to take up a mmiber of mechanicalproblems which the heart presents when regarded asa valvular pump in action. 1. External Phenomena of the Beat.—(a) When theliving heart is observed directly either in a mammalor, better still, in a cold-blooded animal like the frogor terrapin, each beat is seen to begin with a con-traction of the great veins in the neighbor
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
