PEEFACE. 



THESE Lectures, since they were published in the 

 British Medical Journal, have been corrected, 

 and three Appendices have been added to show 

 how the progress of Physiology depends now 

 upon Physics and Chemistry. 



The object of this republication will be 

 obtained, if the idea of the inseparability of 

 matter and force is made clearer to any one ; 

 or even if the confusion that exists in the use of 

 the word force, or the indefiniteness in the use 

 of the word matter, is lessened. 



The confusion regarding the word force partly 

 comes from its use in not less than three dif- 

 ferent senses : firstly, as the cause of motion ; 



237578 



