THE CURVE OF INTRAVENTRICULAR PRESSURE. 19 



evident, on comparison, that the original tracings obtained by 

 Chauveau and Marey (Fig. 6) also nearly represent these. 



The small waves which are seen on the top of the plateau have been 

 explained in several ways. They have been attributed to the vibrations 

 of the auriculo- ventricular valves. By Marey they were ascribed to 



FIG. 12. Intra ventricular pressure curve. Bayliss and Starling. 



waves set up in the large arteries during the systolic output. He 

 supposed that these waves passed back into the ventricle, and were 

 reflected from the ventricular wall and auriculo-ventricular valves. It 

 is highly probable that such vibrations would be produced by the sudden 

 tension of such an elastic system as is formed by the heart and large 

 arteries. Tigerstedt 1 and Porter 2 have attributed the waves to the 

 swing of the instruments employed. Fredericq, 3 d'Espine, 4 and Stefani 5 

 have ascribed them to three successive muscular contractions of the 



FIG. 13. Aortic pressure curve. Bayliss and Starling. 



ventricle. This is a far-fetched explanation, and is controverted by the 

 curves of the negative variation of the heart, obtained with the capillary 

 electrometer by Waller, Bayliss and Starling, and others. 



The plateau and its wavelets are only obtained when the ventricle is 

 filled with blood, and are not seen on curves of contraction obtained 

 from the empty ventricle. 6 It is to be concluded that the plateau is the 

 sign of the sustained tension on the blood by the ventricle wall during 

 the systolic output, and that the wavelets are due to vibrations set up in 

 the elastic circulatory system by the sudden systolic increase of tension. 



The period of rising tension. Part of the period of ventricular 

 systole is spent in raising the tension of the blood up to and above that 

 in the aorta. 



During this period all the valves in the ventricle remain closed, and 

 the capacity of the ventricular cavity does not vary. The muscle bands 



1 "Lehrbuch d. Phys. des Kreislaufes," Leipzig, 1893, S. 101. 



2 Journ. Exper. Med., N. Y., 1896, vol. i. p. 296. 



3 "Trav. du labor. Liege," 1888, tome ii. p. 91. 



4 Rev. de med., Paris, 1882, tome vii. p. 17. 



5 Mem. Accad. med.-cUr. di Ferrara, il 5 Agosto, 1891, p. 69 ; Ceniralbl. f. Physiol., 

 Leipzig u. Wien, 1893, S. 79. 



6 Laulanie", Gmnpt. rend. Soc. de biol., Paris, 1892, p. 557 ; E. Meyer, Arch, fa physioL 

 norm, et path., Paris, 1892, tome xxvi. pp. 670-678; Marey, "Circulation du sang, 

 Paris, 1881, p. 95. 



