CHAPTER XI. 



Study of the chief vascular and respiratory 

 mechanisms: 1. Action of the heart in man. 



Observe the chest wall over the situation of the 

 heart ; notice and feel the impulse or apex beat, 

 strongest at one spot. Apply the ear directly or 

 through a stethoscope over this spot, and make out 

 the two cardiac sounds. 1 Whilst listening to the 

 sounds of the heart feel the pulse of the subject, and 

 determine that the first sound is systolic t.e. t is 

 synchronous with the rise of pressure in the artery 

 due to the contraction of the ventricle. Next 

 apply the button of a cardiograph to the point 

 where the impulse is most distinct, and take a 

 tracing upon a moderately fast drum by the aid of 

 a recording tambour. The breath may be held 

 whilst the tracing is taken, so as to eliminate the 

 movements caused by respiration. 



2. Methods of determining the pressure and 

 velocity of the blood in the arteries. The chief 

 methods used can be studied upon a system of india- 

 rubber tubes through which water is pumped by a 

 Higginson syringe. With this system mercurial and 

 other manometers and the stromuhr and other in- 



1 The second is heard most distinctly over the second right 

 costo-sternal articulation. 



