50 



(figs. 16 and 18). When the heart has recorded a few con- 

 tractions, tie the loop tightly so as to separate the auricles 

 from the sinus. Note and record the result. 



C. CHARACTER OF A SINGLE VENTRICULAR CONTRACTION. 

 After the ventricle has been stopped take a trace on a 

 moderately fast drum (slow-gear large spindle to the smallest 

 on the drum) of the contraction caused by touching the 

 ventricle. The touch will record the moment of stimulation 

 on the drum. Take a time trace in roth sec. and measure 

 the duration of the phases. 



Again put the drum on very slow speed and tie another 

 loose loop round the whole heart, and tighten it so that it 

 exactly separates the auricles from the ventricle. Record the 

 result. CONCLUSION ? 



D. THE EXTERNAL MANIFESTATIONS OF THE CARDIAC CYCLE 



IN MAN. 



1 . The Cardiac Impulse Cardiograph. Get ready and study 

 the mode of action of a cardiograph, which should have a long 

 lever on the recording tambour. Find the position of the 

 cardiac impulse on the front of the chest of a fellow student 

 and investigate its characters. Mark its position with an 

 aniline pencil and then apply the cardiograph with the button 

 upon the impulse. Adjust the pressure of the button by 

 means of the screw till the lever gives the largest possible 

 excursion, and take a tracing on a slow-moving drum. This is 

 best done with the subject leaning forward and to the left. 

 The breath may be held for a few seconds. Take a time 

 tracing in seconds. Make an enlarged drawing of a part 

 of the trace and try to explain the various elevations and 

 depressions. 



2. Sounds of the Heart. With the stethoscope provided, 

 listen over the cardiac impulse and over the middle sternum 

 opposite the second rib. Put a finger on the cardiac impulse 

 and try to time the sounds heard in relationship to this. 

 Note the characters of the sounds. 



