VII 



MECHANICS OF THE HEART 



205 



ventricular relaxation the blood can flow freely from the vein to 

 the auricle, from the auricle to the ventricle, by the negative 

 pressure or aspiration which this exerts during the said phase. 



L. Fredericq, in his studies on 

 dogs (in relation to cardiography 

 of the heart and the venous 

 pulse, 1890-1907), insisted on the 

 virtual identity of the phlebo- 

 grains with the tracings of the 

 variations of blood pressure with- 

 in the right auricle, which he 

 obtained with open thorax, on 

 putting this cavity into direct 

 communication with a sensitive 

 sphygnioscope (Fig. 66). 



To obtain an idea of the in- 

 dividual phases of the cardiac cycle and the oscillations of pressure 

 within the auricles, ventricles, and large arteries, we may avail 



FIG. lit}. Marey's sphygmoscope, which acts as 

 an elastic manometer in connection with 

 a tambour. It consists of a cylindrical 

 glass tube, closed at both ends by rubber 

 stoppers with a hole through the centre 

 of which come two glass tubes. An elastic 

 cap is slipped over the right-hand stopper, 

 h'lled with an anticoagulant solution, and 

 connected with a blood-vessel. The cap 

 reacts to each rise and fall of pressure, by 

 expanding or contracting. The tube on the 

 left-hand side conveys these movements to 

 the tambour. 



FIG. 67. Diagram of cardiac cycle or revolution. The three curves reproduce the tracings of 

 oscillations of pressure obtained simultaneously from the left auricle, left ventricle, and 

 aorta of the dog, by Frederick's method. The duration of the different phases of the cycle, 

 and the time at which the heart-sounds are perceptible, are marked on the abscissae ; the 

 intracardiac and aortic pressures in mm. Hg, upon the ordinates. 



ourselves of a diagram constructed from the data provided by the 

 work of Fredericq, which agree fundamentally with those admitted 

 by all competent physiologists who have occupied themselves with 

 the mechanics of the heart (Fig. 67). 



