CHAPTER I 



INTRODUCTION 



THE content of this little book is founded on three 

 TYNDALL Lectures, given in the Royal Institution, 

 London, on the i4th, 2ist, and 28th of May 1914. 



The aim of these lectures was to give a short 

 review of the new chapters in Biochemistry in 

 which quantitative measurements have been carried 

 out, and subsequently discussed at some length from 

 the points of view adopted in Physical Chemistry. 



As long as only qualitative methods are used in a 

 branch of Science, this cannot rise to a higher stage 

 than the descriptive one. Our knowledge is then 

 very limited, although it may be very useful. This 

 was the position of Chemistry in the alchemistic 

 and phlogistic time before DALTON had intro- 

 duced and BERZELIUS carried through the atomic 

 theory, according to which the quantitative com- 

 position of chemical compounds might be determined, 

 and before LAVOISIER had proved the quantitative 

 constancy of mass. It must be confessed that no 

 real chemical science in the modern sense of the 

 word existed before quantitative measurements 



B 



