7O EXPERIMENTAL PHYSIOLOGY 



ventricle. In a frog, the spinal cord of which has been destroyed, 

 there is usually little or no blood passing through the heart. But if 

 blood is being pumped through, notice the sudden distension (diastole) 

 of each cavity which immediately succeeds its contraction (systole). 



Cut edge of septum. 



^^fc. 



Auricular septum. ^ x^BlBJ^I^gs^ ^ Right auricle. 



Left auricle. 



Aur.-ventr. valve. %3^$3SSH33ISK Bulb. 



Valve. 



Ventricle. 



FIG. 60. Section through heart of frog. Front half seen from behind 

 (Gaupp). The spongy structure of the ventricle is shown, f . 



If the finger is very lightly placed on the ventricle the hardening 

 which accompanies systole may be felt (cardiac impulse). 



Effect of heat and cold on rate of beat. Using a watch, count the 

 number of beats per minute during several minutes and record the 

 average. Now apply, first, an ice-cold and, second, a warmed copper 



Septum of auricles. 



Orifice of pulmonary vein. 

 Right vagus nerve. - 



Left vagus nerve. 



Bidder's ganglion. 

 Ventricle. 



FIG. 61. Heart of frog with left auricle cut open to show the vagus 

 nerves in the auricular septum (Gaupp). -f . 



rod (a) to the ventricle, (b) to one of the auricles, and (c) by turning 

 up the heart, to the sinus. Count the rate immediately after each 

 application, and note down the results. 



Stannius' experiment. Raise the ventricle very carefully without 

 pinching or injuring it in any way, and, after cutting the ligament or 

 fold of pericardium before mentioned, which encloses a small vein, pass 



