654 



DEFICIENT ARTERIALIZATION. [BOOK n. 



These changes in the heart in no way explain the rise of pres- 

 sure ; that is obviously due to a very great increase of peripheral 



A n ft " 



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fif\ I 



FIG. 86. BLOOD-PRESSURE CURVES DURING A SUSPENSION or BREATHING (UNDER 

 URARI). TRAUBE-HERING CURVES. 



The curves 1, 2, 3, 4, 5 are portions selected from one long continuous tracing 

 forming the record of a prolonged observation, so that the several curves repre- 

 sent successive stages of the same experiment. Each curve is placed in its 

 proper position relative to the base line, which, to save space, is omitted ; and 

 it is obvious that, starting from the stage represented by 1, the blood-pressure 

 rises in stages 2, 3, and 4, but falls again in stage 5. Curve 1 is taken from 

 a period when artificial respiration was being kept up, and the undulations 

 visible are those the nature of which has been discussed ; the vagus nerves 

 having been cut the pulsations on the ascent and descent of the undulations do 

 not differ. When the artificial respiration was suspended these undulations dis- 

 appeared, and the blood-pressure rose steadily while the heart-beats became slower. 

 Soon, as shewn in curve 2, new undulations appeared. A little later, the blood- 

 pressure was still rising, the heart-beats still slower, but the undulations still more 

 obvious (curve 3). Still later (curve 4), the pressure was still higher, but the heart- 

 beats were quicker, and the undulations flatter. The pressure then began to fall 

 rapidly (curve 5), and continued to fall until some time later artificial respiration 

 was resumed. 



resistance, the heart contributing to the result only so far that 

 its output does not diminish as the peripheral resistance in- 

 creases, but rather, at first at least, as we have said increases. 

 That the peripheral resistance is due to a large vaso-constriction 

 brought about by the too venous blood stimulating the bulbar 

 vaso-motor centre is shewn by the fact that the rise of pressure 

 is far less, indeed very small, if the cord be divided below the 



