92 



ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



the heart is more fully exposed to the view when the chest is opened? 

 Palpate with the tip of your index-finger the walls of the right and left 

 ventricles, observing in each case the difference in the texture of the 

 cardiac muscle on systole and diastole. Also note the much greater 

 thickness of the left musculature. Observe that the two auricles con- 

 tract practically simultaneously, and that their contraction begins near 

 the orifice of the venae cavse. Likewise, note that the two ventricles 

 contract together as soon as the auricular systole has been completed. 

 Expose the superior and inferior cavse and observe their pulsations 

 (venous pulse). Expose the aorta and pulmonary artery and study their 

 pulsations (arterial pulse). 



Place the tip of your index-finger upon the surface of the left auricular 

 appendix. Press downward. Do you feel the flaps of the mitral valve 

 hitting against your finger? Repeat this observation on the opposite 

 side. Blow a spray of albulin upon the heart to prevent its drying. 



FIG. 57. CARDIOMETER. 

 The heart is inserted through a perfora- 

 tion in rubber membrane (K) into cavity 

 of a hemispheric glass capsule (C). The 

 latter is connected with a recording tam- 

 bour (T). 



FIG. 58. CLAMP FOR PRODUCING HEART- 

 BLOCK. ( After Erlanger.') 



Discontinue the artificial respiration for a brief period of time until 

 the heart has been markedly slowed. Again study the progress of the 

 wave of contraction and note the gradual change in the color of the 

 heart. Its venosity is most clearly betrayed by the left auricle, the 

 color of which gradually changes from bright red to dark purple. Ex- 

 plain this phenomenon. Resume artificial respiration. Allow a few 

 drops of a slightly warmed saline solution to fall upon the heart. Note 

 the increase in its frequency. 



Procure a small cardiac plethysmograph, usually consisting of a hemi- 

 spheric capsule of glass the orifice of which has been closed with a rubber 

 membrane. Incise the rubber membrane near its center, and push the 

 ventricular portion of the heart through this opening into the cardiom- 

 eter. Connect the tubular outlet of the latter with a recording drum 



