LABORATORY MANUAL OF PHYSIOLOGY. 



tambour to the apex impulse. A curve will be written on the 

 drum. Make a number of tracings from the same individual, 

 varying the pressure of the cardiograph against the chest wall 

 and varying the position of the subject of the experiment. 



Compare the different tracings taken from the same individual 

 with each other. Does the curve recorded consist of a single wave 

 or of a wave with crests and depressions? Note the notches and 

 apices of the waves which occur in all the tracings and the points 

 in the curve in which they occur. 



Take a series of tracings from another individual and compare 

 the essential features of these with those of the other series. 



With a stethoscope listen over the cardiac area for the heart 

 sounds. Palpate the pulse at the wrist or over the carotid at the 

 same time. How many different sounds do you hear ? What are 

 their characteristics in pitch, duration, and synchronism with the 

 pulse wave ? 



At what part of the cardiac area is the first heart sound best 

 heard ? Where is the second sound most distinctly heard ? What 

 factors enter into the production of the heart sounds ? Where can 

 the mitral-valve factor be best made out to differentiate it from 

 the other valves? The tricuspid- valve factor? The aortic-semi- 

 lunar-valve factor ? The pulmonary-semilunar- valve factor ? Ex- 

 plain why you listen in certain regions for the different valve 

 sounds. 



While a cardiogram is being made, listen to the heart sounds. 

 Compare the sounds, in point of time, with the features of the car- 

 diogram tracing. 



While a sphygmogram is being taken listen to the heart sounds. 



XXIII. THE VASOMOTOR MECHANISM. 



1. The General Controlling Centre in the Medulla. Anaes- 

 thetize a large frog lightly with ether. Cut both vagus nerves, in 

 order to exclude changes in the heart-beat, through inhibition or 

 augmentation, from the result. Carefully avoiding hemorrhage, 

 expose the brain and upper part of the cord. 



[no] 



