iv DESCARTES' DISCOURSE ON METHOD 185 



modern language, and by the aid of modern con- 

 ceptions. 



Most undoubtedly, the digestion of food in the 

 human body is a purely chemical process ; and the 

 passage of the nutritive parts of that food into the 

 blood, a physical operation. Beyond all question, 

 the circulation of the blood is simply a matter of 

 mechanism, and results from the structure and 

 arrangement of the parts of the heart and vessels, 

 from the contractility of those organs, and from 

 the regulation of that contractility by an auto- 

 matically acting nervous apparatus. The progress 

 of physiology has further shown, that the con- 

 tractility of the muscles and the irritability of the 

 nerves are purely the results of the molecular 

 mechanism of those organs ; and that the regular 

 movements of the respiratory, alimentary, and 

 other internal organs are governed and guided, as 

 mechanically, by their appropriate nervous centres. 

 The even rhythm of the breathing of every one of 

 us depends upon the structural integrity of a par- 

 ticular region of the medulla oblongata, as much 

 as the ticking of a clock depends upon the integ- 

 rity of the escapement. You may take away 

 the hands of a clock and break up its striking 

 machinery, but it will still tick ; and a man may 

 be unable to feel, speak, or move, and yet he will 

 breathe. 



Again, in entire accordance with Descartes' 

 affirmation, it is certain that the modes of motion 



