270 MANUAL OF PHYSIOLOGY. 



sacks filled with air, whence the pressure changes are commu- 

 nicated to an ordinary " tambour," and registered on a smoked 

 surface. 



Of the whole period of the cycle the passive interval or pause is 

 the longest and the most variable, for in ordinary changes in the 

 heart's rhythm it is the pause that varies. Next in duration is 

 the ventricular systole, while the shortest is the auricular systole. 



The following figures give approximately the proportion of time 



FIG. 119. 



Curves drawn on a moving surface by three levers, which are connected with the in- 

 terior of the heart, viz.: Upper line shows the changes of pressure occurring in the 

 right auricle; centre line shows the pressure changes within the right ventricle; lower 

 line shows the changes of pressure occurring in the left ventricle. (The smoked surface 

 is moved from right to left.) (After Chauvian.) 



occupied by each part of the cycle in the case of a horse, whose 

 intra-cardiac tension was registered in a manner just referred 

 to, while his heart beat about fifty times in a minute: 



