6o 



PRACTICAL PHYSIOLOGY 



dividing into two branches, each of which again 

 soon divides into three (Figs. 40, 41, and 43). 



Right auricle . 

 Bulbusaortae 



Left auricle. 



Ventricle. 



FIG. 40. FROG'S HEART ; VENTRAL ASPECT (CKER). 



Effect of heat and cold on rate of beat. 



Count the number of beats per minute. Now apply, 

 first, a cooled and, second, a warmed wire (a) to 

 the ventricle, (<$) to the auricles, (r), by turning up 

 the heart, to the sinus. Count the rate immedi- 



Left superior vena cava ... 



Left auricle.. 

 Opening from sinus into 



right auricle.. _- 



Sinus venosus cut open..---" 



Pulmonary vein. 

 ..Right superior vena cava. 



. .Right auricle. 



Ventricle. 

 Inferior vena cava. 



FIG. 41. FROG'S HEART; DORSAL ASPECT (ECKER). 



ately after each application. If desired the effects 

 may be recorded in the manner described below. 

 Stannius' experiment. Raise the ventricle 



