64 



XVII 



Each dissection is to be carefully demonstrated to one of 

 the instructors before beginning- the dissection of a new part. 



261. Dissection of Frog's Heart. With a pair of 

 strong scissors and forceps cut through the pectoral girdle. 

 Remove the sterum arid expose the heart, cut carefully through 

 the pericardium and note the division of the heart into ven- 

 tricle, auricles, and truncus arteriosus. (Do not remove the 

 heart until the vagus nerve has been dissected). 



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Fig. I 



Fig. 1. Dissection of the frog's heart showing the relationship of the cavi- 

 ties and the principal blood vessels. 



Raise the apex of the ventricle slightly and note a delicate 

 band of connective tissue binding the ventricle to the body, 

 (the frenum). The ventricle is of a conical shape and is 

 usually of a paler color than the auricles. It has thick walls. 



The auricles are two in number although externally the 

 division is not easily apparent. The right is larger than the 

 left and both are usually engorged with blood. The walls of 

 the auricles are thin. 



