HEART ACTION 155 



and ventricle is brought into view. Note that one of its two 

 flaps lies between auriculo-ventricular opening and origin of 

 aorta. 



17) Slit aorta between two semilunar valve flaps: 



a) Compare aorta with pulmonary artery and with larger 

 veins, with special reference to thickness, texture and elasticity. 



b) Note coronary arteries opening into dilatations of aortic 

 wall above semilunar flaps. 



Heart Action 



Materials and apparatus: Frog; 2 sheep's hearts; a piece of 

 sheet cork or of thin board with ^ in. hole cut in it; micro- 

 scope; circulation apparatus made from bulb syringe; funnel 

 of glass or tin; 2 feet of i/4 in. rubber tubing; 10 inches of 

 1 in. sap tubing; several feet of glass tubing, some ^4 i n -> 

 some x /2 in.; glass nozzle made of glass tubing drawn out in 

 flame; a piece of sheet lead such as comes in tea chests; 

 dissecting instruments; a circular piece of glass l 1 /^ in. in 

 diameter, cemented into a short tin tube to form a window; 2 

 basins. 



1) Wrap frog in damp cloth and then in tea lead, leaving 

 one foot outside of lead. Fasten it to perforated sheet cork or 

 board and tie toes to pins so that web foot is spread over hole. 

 Clamp in place on microscope stage and focus carefully on web. 

 Note movement of blood corpuscles; arteries, through which 

 blood is passing toward thin-walled capillaries ; veins into which 

 blood from capillaries is passing; rapidity of movement of red 

 blood corpuscles, 1 their position in blood stream and bending at 

 arterial branches; movement of white blood corpuscles and 

 their behavior in blood stream. 



2) To demonstrate pumping action of heart, carefully re- 

 move sheep's heart from pericardium. 



a) Aortic valve: Cut off aorta 1 in. above valve. Tie into 

 it a piece of glass tubing, down which pour water. Note 

 efficiency of valve. 



Tie a glass or tin funnel into one pulmonary vein and 

 close the other by tying it. Fill funnel with water. Squeeze 

 ventricles with hand and note results. 



1 The frog's red blood corpuscles differ from the human in that 

 they are oval and have very large nuclei. 



