334 LAY SERMONS, ADDRESSES, AND REVIEWS. [xiv. 



of its weights and its wheels ; so that, so far as these are concerned, it 

 is no necessary to conceive any other vegetative or sensitive soul, nor 

 any other principle of motion, or of life, than the blood and the spirits 

 agitated by the fire which burns continually in the heart, and which 

 is no wise essentially different from all the fires which exist in inani- 

 mate bodies/' 1 



The spirit of these passages is exactly that of the 

 most advanced physiology of the present day; all that 

 is necessary to make them coincide with our present 

 physiology in form, is to represent the details of the 

 working of the animal machinery in modern language, 

 and by the aid of modern conceptions. 



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 automa- 

 tically acting nervous apparatus. The progress of phy- 

 siology has further shown, that the contractility 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, ali- 

 mentary, 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 particular 

 region of the medulla oblongata, as much as the ticking 

 of a clock depends upon the integrity 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, 



1 "Traite de l'Hommc," p. 427. 



