CHAPTEE XXVII 



THE RELATION OF RESPIRATION TO OTHER PROCESSES IN THE BODY 



WE shall in this chapter treat of the relationship between respira- 

 tion and the circulation, and between respiration and metabolism, 

 and in conclusion deal with certain pathological conditions, which 

 are important for the light they throw upon physiological processes. 



The Effect of Respiration on the Circulation. 



The main effect of respiration on the circulation is shown in the 

 accompanying figure (fig. 303). It will be noticed that the arterial 



Fia. 303. Comparison of blood-pressure curve with curve of intra-thoracic pressure. (To be read from 

 left to right.) a is the curve of blood-pressure with .its respiratory undulations, the slower beats 

 on the descent being very marked ; b is the curve of intra-thoracic pressure obtained by connecting 

 one limb of a manometer with the pleural cavity. Inspiration begins at i and expiration at e. 

 The intra-thoracic pressure rises very rapidly after the cessation of the inspiratory effort, and then 

 slowly falls as the air issues from the chest ; at the beginning of the inspiratory effort the fall 

 becomes more rapid. (M. Foster.) 



pressure rises with inspiration and falls with expiration, but that the 

 two events are not quite synchronous, the rise of pressure beginning a 

 little later than the inspiratory act, and the fall a little later than 

 the expiratory act. 



It will also be scon that the heart beats more rapidly during tho 



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