THE CIRCULATION OF THE BLOOD AND LYMPH 87 



that the ventricular pressure, after reaching its maximum, 

 maintained itself there throughout the greater part of the 

 systole. The tracings yielded by most of the manometers with 

 air transmission (Fig. 28) show the same suddenness in the first 

 part of the upstroke and the last part of the descent that is, 

 the same abruptness in the beginning of the contraction and the 

 end of the relaxation. But they differ totally in the inter- 

 mediate portion of the curve, which, climbing ever more gradually 

 as it nears its apex, remains but a moment at the maximum, 

 then immediately descending forms a ' peak/ and not a plateau. 

 Without entering further into a technical discussion, we may 

 say the bulk of the evidence goes to show that the plateau is 



FIG. 27. SIMULTANEOUS RECORD OF PRESSURE IN LEFT VENTRICLE (V) AND 

 AORTA (A). (HURTHLE.) 



The tracings were taken with elastic manometers ; o indicates a point just before 

 the closure of the mitral valve ; i, the opening of the semilunar valve ; 2, begin- 

 ning of the relaxation of the ventricle ; 3, the closure of the semilunar valve ; 

 4, the opening of the mitral valve. The ventricular curve shows a ' plateau.' 



not, as the advocates of the peak have claimed, an artificial 

 phenomenon, but does in reality correspond to that continuation 

 of the systole of the ventricle, that dogged grip, if we may so 

 phrase it, which it seems to maintain upon the blood after the 

 greater portion of it has been expelled. 



This conclusion is essentially in accordance with the results of 

 Chauveau and Marey, obtained long ago by means of their ' cardiac 

 sound,' which was in principle an elastic manometer (Fig. 29). 



It consisted of an ampulla of indiarubber, supported on a frame- 

 work, and communicating with a long tube, which was connected 

 with a recording tambour. The ampulla was introduced into the 

 heart through the jugular vein or carotid artery in the way already 

 described. Sometimes a double sound was employed, armed with 

 two ampullae, placed at such a distance from each other that when 



