ARTERIAL BLOOD PRESSURE IN MAN 263 



6. After 10 to 15 seconds cut the left vagus, marking the time of cutting 

 with the same care on the tracing. As soon as the nerves are cut, the heart- 

 rate will be observed to increase sharply and the blood pressure to rise. 

 The respirations also change in rate and depth, a fact which can be noted by 

 its influence on the blood-pressure tracing. 



7. Now lift up the distal end of the divided left vagus, and stimulate 

 it with an electric current of the strength which previously just produced 

 inhibition. Repeat the experiment on the proximal end of the divided vagus. 

 The stimulation of the proximal end of the vagus produces no direct effect 

 on the heart rate when both vagi are cut, but does produce profound 

 changes on the blood pressure owing to vaso-motor effects. 



8. If the rabbit is used, stimulate the depressor nerve, which produces 

 marked fall in blood pressure from reflex effects. 



9. Repeat the stimulation of the central end of the sciatic as described 

 in 3, now that the vagus nerves are cut. The stimulation of this nerve 

 no longer produces changes in the heart-rate, but the blood pressure 

 is influenced as before, showing that the vaso-motor centers are reflexly 

 stimulated. 



10. When you have finished the outline of experiments, give an excess of 

 the anesthetic to kill the animal and continue the record until the animal is 

 dead. The blood pressure will fall rapidly, the heart-rate will become slower 

 but does not cease for a long time. 



Should a clot form in the cannula, put a bulldog forceps on the artery, 

 disconnect the manometer tube, and wash the clot out by a stream of liquid 

 from the pressure bottle. Use care not to allow this fluid to enter the ex- 

 posed wound. 



Represent the results of each individual experiment in the above series 

 in tabulated form which shall show: i, the blood pressure and heart-rate just 

 before each experiment; 2, during the experiment; and 3, at different times 

 after the experiment until the normal is reached. After the facts are taken 

 from the tracings and arranged in tabular form, make a study of these facts 

 and draw all the conclusions you can concerning the nervous regulations of 

 the heart and of the blood pressure. Make written report. 



20. Arterial Blood Pressure in Man. The arterial blood pressure 

 in man can be measured only indirectly by measuring the pressure which it 

 takes around the arm completely to close the artery. Some form of the 

 Riva-Rocci apparatus, preferably Erlanger's sphygmomanometer, should 

 be used. Adjust the rubber bag and leather sleeve of the Erlanger appara- 

 tus, figure 189, to an arm, and connect it to the sphygmomanometer, set the 

 valve, and quickly pump the pressure up to a point which occludes the pulse. 

 Adjust the writing point of the recording tambour to the smoked paper on 

 the cylinder, then lower the pressure by lo-mm. steps until the first pulse 

 appears. Now proceed with care, changing the pressure by 5-mm. steps 



