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 236 LECTURE V. 



The blood returning from all parts of the 

 body is, in the higher classes of animals, 

 propelled from the right side of the heart 

 through the lungs. To observe the circum- 

 stances resulting from the conjoined actions 

 of the heart and respiration, Mr. Hunter 

 contrived a pair of bellows by which he 

 could maintain the latter process in an arti- 

 ficial manner, and thus he was enabled to 

 observe how greatly the heart's action de- 

 pends on its continuance. He says, " the 

 nearest dependence of the heart is upon the 

 lungs, for a stoppage of respiration pro- 

 duces a stoppage of circulation ; and a re- 

 newal of the former is attended with a re- 

 newal of the latter. Thus, in my experi- 

 ments with artificial breathing, the heart 

 soon ceased to act, whenever I left off act- 

 ing with my bellows; and upon the renewal 

 of artificial breathing, it in a very short 

 time renewed its action, first by slow de- 

 grees, but becoming quicker and quicker 

 till it came to its full action." Mr. Hunter 

 displays the subject of the structure and 

 uses of the lungs, according to our present 

 notions. He says, " that as the function of 



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