SIGNIFICANCE OF PULSE RATE BUCHANAN. 505 



if the action of the vagus on the heart were prevented, e. g., by the 

 administration of atropine; whether in such case the frequency of 

 beat was reduced to the same extent, and if so, secondly, whether 

 under a continuation of the treatment heart acceleration occurred, 

 and occurred as promptly, on awakening from hibernation. If in 

 spite of such procedure the animal when awake still succeeded in 

 regulating its temperature, we should know that other agencies than 

 the central nervous system were more intimately concerned in adapt- 

 ing the heart to meet the demands made upon it. We should then 

 be in a better position than we are now to discuss whether the power 

 which we have shown to be exercised by the heart in the different 

 species of warm-blooded animals of complying with the demands 

 made upon it, not on occasion only but for life, has been evolved 

 under nervous control. 



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