8 PHYSIOLOGICAL CHEMISTRY. 



The discussions of the earlier part of the eighteenth century 

 placed in clear light finally the full meaning of the doctrine 

 of the Indestructibility of Matter. These later discussions 

 developed a new doctrine, that of the Conservation of Energy, 

 the recognition of which played no' small part in the gradual 

 advance of physiological as well as physical science. 



It is the intention of the following chapters to present the 

 fundamental facts and theories of physiological chemistry in 

 the simplest possible manner. Much matter found in the 

 larger hand-books must necessarily, -therefore, be omitted from 

 a work of this elementary character. But enough will be 

 given to furnish the student, it is hoped, a satisfactory view of 

 that which is most important in the science at the present time. 

 It will be found convenient to make four general divisions of 

 the subject, as follows : 



Section I. The Nutritives and Related Substances. 



Section II. Ferments and Digestive Processes. 



Section III. The Chemistry of the Tissues and Secre- 

 tions of the Body. 



Section IV. The End Products of Metabolism. Ex- 

 cretions. Energy Balance. 



