285. Artificial circulation scheme. E.xamine the scheme. follow- 

 ing the description given in the Harvard Apparatus Company Cata- 

 logue, and make a diagram labelling the features presented. Fill 

 with distilled water, tipping the tube so as to allow escape of air 

 through the arterial path, and attach the manometers filled with 

 Hg. connected with the tubes of the scheme by water. Note espe- 

 cially the following: Effect of ( i ) increasing the rate of heart beat 

 on (a) arterial pressure, (b) venous pressure, (c) character of 

 flow. (2) Pulse in the aorta. (3) Action of the mitral and 

 aortic valves. 



286. Graphic record of blood pressures. Ulood pressures of 

 living animals may be estimated and recorded by various methods. 

 The principles involved can be determined from records given 

 by the artificial circulation scheme. Place a writing lever in the 

 arterial manometer from which the thistle tube has been removed, 

 and adjust against a drum. (See demonstration.) Take a 

 record showing the effect of ( I ) a rapidly beating heart on the 

 blood pressure, (a) with high and (b) with low capillary resistance; 

 (2) -a slow beating heart with (a) high and (b) low capillary 

 resistance. A base line should be drawn showing the point of zero 

 blood pressure, and a time curve (in seconds) taken from the desk 

 binding posts. 



287. Pulse record. Sf>h\gmograph tambour. Examine the in- 

 strument, and set up as in the demonstration, cementing the alu- 

 minum angle to the rubber membrane and using a straw for the 

 writing lever. Draw. 



Cover a small thistle tube with rubber membrane on which has 

 been cennented a bone button. Connect the tambour by rubber 

 tubing with a side branch and clamp. Place the thistle tube over 

 the "aorta" of the circulation scheme and take a record of its pulse 

 with ( i ) slow heart with ( a ) large and ( b ) small capillary resis- 

 tance. (2) Rapid heart with (a) small and (b) large capillary 

 resistance. A time curve (seconds) should be recorded at the same 

 time. 



288. Human pnlsc. Place the thistle tube without the button 

 over the carotid artery just below the angle of the jaw, having the 

 side branch of the connecting tube open. Adjust against a slow 

 moving drum. Now close the side and record. If no pulse 

 shows, adjust the thistle tube until the correct spot is obtained. 

 Compare the curve with that obtained from the artificial circula- 

 tion scheme. 



87 



