474 APPENDIX 



Now, having everything ready, make a series of (1) normal sphygmo- 

 grams around the drum (pulse-rate of 75, high capillary resistance). 

 Analyze the curve. Observe (A) the speed of the uprise of the writing- 

 lever; (B) the speed of its downfall; (C) the dicrotic notch. (2) Make 

 a series of sphygmograms with a low capillary resistance and compare,, 

 in whole and in part, with the normal curve. (3) Make a series with 

 a pulse-rate lower than 75. Make these three sets of sphygmograms 

 directly under each other so that they may be the better compared, the 

 drum-speed being constant. Note the characteristics of each, and 

 study out exactly what each means in the body. 



The pathological sphygmogram records abnormalities in the cardiac 

 valves: stenosis and incompetency of both the auriculo-ventricular and 

 the aortic valves. These make up the four common valvular heart- 

 lesions found in man. 



Expt. 24. Incompetency of the Auriculo-ventricular or Mitral Valve. 

 To imitate this condition in the schema, carefully draw out the left- 

 hand valve-tube and turn the thin rubber covering so that it no longer 

 protects the hole in the glass from regurgitation of the "blood." Re- 



FIG. 260 



Normal sphygmogram made on the artificial circulation-apparatus. The capillary resistance 

 and the blood-pressure both were high. To be read from left to right. Time-line is in seconds. 



place and make a series of sphymograms at the normal rate, and com- 

 pare with the normal curve. Note that the curve is different from the 

 normal, because much of the "blood" now regurgitates from the ventricle 

 into the auricle at each beat. The shape of the curve may not be much 

 different from the normal, but the tracing is narrower vertically. Re- 

 place the rubber on the valve-tube in its normal place (Fig. 261). 



Expt. 25. Aortic incompetency is produced similarly on the other 

 valve. Make a series of curves and study their abnormal characteristics. 

 Note the low pressure in the arteries and its great variation ; these make 

 a soft and bounding "gaseous" pulse. Replace the valve-dam in nor- 

 mal position. 



Expt. 26. Mitral stenosis is produced by removing the valve-tube 

 and loosely tying a thread over its orifice so that less "blood" than 

 normally may pass through. Be careful not to tie the thread too tightly. 

 Make a series of sphygmograms and compare them with norm. Observe 

 the shape of the curve. Restore the schema to its normal condition. 



Expt. 27. Aortic stenosis is produced similarly on the aortic valve. 

 Make a series of curves and compare them with the normal sphyg- 



