AN INTRODUCTION TO THE 

 STUDY OF BIOLOGICAL CHEMISTRY 



CHAPTER I. 



THE GENERAL SCOPE OF BIOCHEMICAL STUDY. 



THE study of biological chemistry, which comprises the 

 systematic investigation of the chemical processes which 

 take place within living objects, is of comparatively recent 

 origin. Up to nearly the end of the eighteenth century, 

 the standard text-book of chemistry most usually referred 

 to was one by Nicolas Lemery, entitled " Cours de Chymie," 

 originally published in 1675. In this book the subject 

 of chemistry is subdivided into three parts, dealing re- 

 spectively with the composition of animal, vegetable, and 

 mineral substances. During the last quarter of the 

 eighteenth century chemical studies received a consider- 

 able stimulus from important researches published by a 

 number of distinguished investigators, who succeeded in 

 isolating in a pure state several substances from both 

 plants and animals. Products of this character were 

 shown by Lavoisier (17431794) to contain carbon, hydro- 

 gen, and generally oxygen, and to possess the property of 

 charring when heated and giving rise to volatile products 

 of decomposition, in which respect they differed markedly 

 from substances of mineral origin. From this time 



