282 MOVEMENT 



The auricle, which commences to fill in the 2nd 

 position of the series, is in process of contraction 

 during the 6th, 7th, and 1st. Now, during the stage 

 of auricular contraction, the ventricle may be seen 

 gradually rilling, so that in position 1, when the 

 auricle has reached the climax of its contraction, the 

 ventricle has attained to its maximum of repletion. 

 The alternations between the diastolic and systolic 

 periods of the two chambers of the heart are therefore 

 perfect. 



The duration of these phases can be calculated 

 almost exactly from the number of positions which 

 correspond to each stage. The apparatus produced 

 10 images per second, and since 7 images sufficed 

 to rejDresent an entire cardiac cycle, the latter 

 may be concluded to last -j 7 g of a second. In 

 the same way to the systole of the ventricles may 

 be assigned a duration of ^ of a second, and to the 

 diastole ^*. 



These primary notes on the changes in shape of the 

 cavities of the heart will be supplemented by the 

 following experiment. 



Variations in Shape and Capacity of the Auric es and 

 Ventricles during a Cardiac Cycle. — The surface of the 

 heart can be rendered photogenic by means of a very 

 simple device ; it suffices to paint it with rather a thick 

 coat of Chinese white. The heart being rendered thus 

 quite white, the play of light and shade displays the 

 alterations in shape and capacity of the different 

 cavities. If a chronophotograph be taken of such a 



* These measurements do not pretend to rival in exactness those 

 derived from the graphic method, which are almost infinitely accurate. 

 When the commencement and termination of a phenomenon is 

 measured by means of a discontinuous serie9 of images, there may be 

 an error us regards both these stages. The commencement and 

 termination may occur between two exposures of the photographic 

 plate, and it is impossible to say exactly when they occur. 



