144 AMPHIBIA (the frog) 



(b) The Auricles. At the anterior and dorsal end of the 



heart, find the two auricles. 



(1) Shape? 



(2) Size? 



(3) Color? 



(4) Are the walls thick or thin as compared to the ven- 



tricle? 



(5) Use? 



(c) Conus Arteriosus. The conus arteriosus originates 



from the right side of the base of the ventricle, 

 soon divides into two branches. Each divides 

 into three, the posterior uniting in the dorsal aorta. 



(d) Dorsal Aorta. Trace the principal branches. 



(1) What organs or parts of the body do they supply? 



(2) Notice that these arteries are firm, elastic blood- 



vessels. 



(e) Veins. The flabby blood-vessels are veins. As you 



traced the arteries from the heart, now trace the 

 flabby veins to the heart. 



(1) From what organs or parts of the body do they 



originate? 



(2) Where do they unite? 



(3) Where do they empty into the heart? 



(f) Sketch or make diagram of the circulatory organs, 



showing pericardium, ventricle, auricles, conus 

 arteriosus, and the principal arteries and veins. 

 Indicate upon each artery the organ supplied, and 

 upon each vein the organ from which the vein 

 comes. 

 4. Reproductive and Excretory Organs. 



(1) The Reproductive Organs. If the specimen is a female, 



the reproductive organs will appear as long coiled 

 tubes, filled with eggs in the breeding season. If a 

 male, the reproductive organs will appear as a pair 

 of yellowish bodies just below the kidneys. Do 

 not confuse the reproductive organs with the slender 

 branched fatty bodies which are generally present. 



(2) The Excretory Organs. The kidneys are two flat 



bodies along the back-bone. 



