52 



3. Do the movements of the heart cause movements of the air 

 in the air passages ? Cardio-pneumatic Movements. 



Fill the mouth, nose and pharynx with tobacco or other 

 smoke. Hold the nostrils. Insert a glass tube drawn to a 

 somewhat fine point into the mouth. Stop breathing and 

 keep the glottis open. Note any movement of the smoke in 

 the tube, and time it with the cardiac impulse. CONCLUSIONS ? 



B. Circulation in the Blood Vessels. 

 I. Blood Pressure. 



1. General Distribution. Examine the schema of the blood 

 vessels made of elastic tubes given you, and identify the 

 parts representing arteries, capillaries and veins. Attach the 

 arterial end to the water tap, and fix vertically in stands the 

 two glass tubes connected with the arteries and veins respec- 

 tively. Cautiously turn on the water and measure the pressure 

 in the arteries and in the veins, and calculate it in mm. of 

 mercury. Note the effect of (a) varying the force of inflow 

 by turning off and on the tap, (6) varying the resistance to 

 outflow by constricting the arteriole tubes. 



2. The Arterial Pulse. 



(1) With the finger, compress and relax the arterial tube 

 near the tap at regular rhythmic intervals of about a second, 

 so as to imitate the interrupted inflow of blood from the 

 heart. Note the effect of this upon the arterial and venous 

 pressures, and study the further effect of constricting the 

 arterioles. 



(2) Place a finger on the arterial tube and note the expan- 

 sion, the pulse, with each inflow. Study the same thing 

 in the venous tubes. Explain any difference which may be 

 observed. 



(3) Radial Pulse. Place a finger of the left hand on the 

 radial artery at the right wrist while feeling the cardiac 

 impulse with the right hand, and note what is felt in the 

 artery. Determine whether the change is simultaneous with 

 the cardiac impulse. 



