THE HISTORY OF PHYSIOLOGY 7 



and non-mechanists, the history of physiology 

 displays uninterrupted progress in the suc 

 cessful application of physical and chemical 

 methods to physiological problems. To take 

 only a few examples, the principles of 

 mechanics were applied by Borelli to eluci 

 date the action of the muscles on the limbs. 

 Kepler applied the principles of optics to the 

 action of the eye in vision. Harvey estab 

 lished and analysed the facts relating to 

 circulation of the blood by the application 

 of purely physical observation and reason 

 ing. As a result of the great advance in 

 chemistry at the end of the eighteenth 

 century the fundamental facts with regard 

 to respiration and its relation to nutrition 

 and animal heat were discovered ; and since 

 then the application of chemical methods 

 to physiological problems has been continued 

 with unbroken success. In more recent 

 times the advance of physical chemistry 

 has placed new and powerful weapons in the 

 hands of physiologists. It is doubtless the 

 case that the application of chemistry to 

 physiology has also shown us that the 

 chemistry of life is far more complex than 



