LABORATORY MANUAL OF PHYSIOLOGY. 



The manometer tubing is clamped off and the pressure in the 

 manometer and connections is raised to approximate the estimated 

 arterial pressure of the rabbit. 



The artery cannula is then filled with o.8-per-cent solution of 

 NaCl, care being taken to get rid of all air bubbles both in the 

 cannula and manometer connections. The manometer tube is then 

 connected with the arterial cannula, the clamp is removed from the 

 tubing and from the artery at the same time, and the pressure in 

 the artery is transmitted through the tubing to the mercury in the 

 proximal limb of the manometer which falls and rises in the distal 

 limb. 



Before the mercury in the manometer was put under extra press- 

 ure, a base line should have been drawn around the drum to in- 

 dicate the atmospheric pressure. The height of the tracing above 

 this base line, multiplied by 2, gives the pressure in terms of 

 mercury. 



2. Note the rise and fall of pressure synchronous with the heart- 

 beat. Where the beat is rapid, as it is normally in the rabbit, the 

 excursion of the manometer style is not an accurate index of the 

 variations of pressure. The inertia of the mercury is too great to 

 follow exactly small and rapid variations in pressure. 



Note the larger waves in the tracing. These are due to changes 

 in arterial pressure brought about by inspiration and expiration. 

 Observe the respiratory movements and compare them with the 

 respiratory waves of the tracing. Is there a rise or fall of blood 

 pressure with inspiration? with expiration? Does the change 

 correspond exactly to the respiratory movement? 



Are there any other pressure waves in the tracing aside from the 

 pulse waves and the respiratory waves ? Explain. 



3. Effect of Vagus Stimulation. While the tracing is being 

 taken, tie one vagus with two ligatures and cut between. Note any 

 change in the pressure tracing. Mark on the tracing the place at 

 which the nerve was tied and cut. 



(a) Stimulate the peripheral end of the cut nerve with a weak 

 tetanizing current. Is there any effect on blood pressure or upon 



t"4] 



