THE CIRCULATION 101 



valve, and the one distally to the bulb the aortic semilunar valve. The 

 side branch from the ventricle may be connected by means of a thistle 

 tube with a membrane manometer, and may thus be used to register 

 the changes in pressure in the ventricle. In a similar manner the 

 changes in pressure in the aorta may be recorded (arterial pulse). 

 Beyond the aorta lies the remaining portion of the arterial system, to 

 which there is attached a mercury manometer for measuring the arterial 

 pressure. Into the dish opens the venous system. It is equipped with 

 a mercury manometer for measuring the venous pressure. Between 

 the arteries and veins are the capillaries, represented in the schema by 

 a short piece of porous bamboo, and a side branch bearing a clamp. 



FIG. 63. MORE RECENT SCHEMA OF THE CIRCULATION. 



The action of the heart is here imitated by a tambour, rhythmically compressed by 

 hand. The veins empty their contents into a receptacle (right auricle) fastened to the 

 side of the upright stand. (Harvard Apparatus Cp.) 



A. Normal Circulation. Dip the inlet and outlet tubes of this 

 system into the water in the basin and pump gently with the rubber 

 bulb until the different tubes have been rilled with water. Clamp the 

 side branch between the arteries and veins. Pump gently at the rate 

 of about sixty times in a minute, and observe the following: 



(a) The action of the valves, 



(b) The arterial pressure and its changes, 



(c) The venous pressure, 



(d) The pulse in the aorta, and 



(e) The character of the flow from the veins. 



Open the clamp slightly, so as to simulate dilatation of the arterioles, 

 and pump as before. What is the effect of this procedure on the arterial 

 and venous pressures and on the character of the venous flow? 



