40 PHYSIOLOGY FOR -THE LABORATORY. 



left ventricle as you did into the right and compare the 

 valves with those of the right ventricle. 



IV. THE SEMILUNAR VALVES AT THE BASE OF THE 

 AOKTA. 



Find the opening of the aorta into the left ventricle and 

 study the semilunar valves as you did those at the base 

 of the pulmonary artery. 



E. The Valves in the Veins. 



Material. The heart and blood-vessels of a calf. 

 Apparatus. Knitting needle. 



If the veins are still attached to the specimen, try to 

 find the valves in them by passing down a small probe, as 

 a knitting needle. 



a. In what direction is the blood flowing in the veins ? 

 In what direction do the valves prevent flow? 



b. Compare their action with that of the semilunar 

 valves in the arteries. 



Remove the heart and reserve the lungs and trachea 

 for study another time. 



F. The Beating of the Heart. 



Materials. A frog. Chloroform. 20 c.c. normal salt solution. 

 Apparatus. Watch crystal. Watch. Bunsen burner. 



Kill a frog with chloroform, and as soon as it is dead and 

 the limbs are stiff make a cut along the ventral median 

 line, cutting through the breast-bone. Take care not to 



