40 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



loosely combined oxygen atoms in the respective molecules 

 combine together to form a molecule of ordinary oxygen, 

 thus : 



3 + H 2 2 = H 2 + 20 2 



These are typical cases of oxidation, the opposite process 

 to reduction. 



We shall see later that this special activity of nascent 

 oxygen is of very great importance in connection with a set 

 of changes brought about by a class of enzymes known as 

 oxidases. 



The study of the action of elements in the nascent state 

 leads to the conclusion that the atom of an element is in 

 general incapable of a separate existence, and the atom has 

 therefore been defined as the smallest portion of an element 

 which can enter into or be expelled from a compound. 



A molecule is defined as the smallest portion of an element 

 or compound which is capable of a separate existence. 



Certain exceptional cases exist where the molecular 

 weight of an element is found to be identical with its 

 atomic weight, but these do not affect the general conclusions. 



We may now proceed to the application of these funda- 

 mental chemical laws to that branch of the science known as 

 organic chemistry, so called because it deals with the sub- 

 stances elaborated to a large extent by living or organic 

 matter, as distinguished from the constituents of the inorganic 

 or mineral world. 



It was at one time thought that organic compounds, pro- 

 perly speaking, could only be produced by vital energy. The 

 synthesis of a characteristic vital product, viz., urea, by Wohler 

 in 1828 broke down this distinction, and since then, out of the 

 countless substances included under the science of organic 

 chemistry, although many are natural products, many have 

 only been prepared in the laboratory and are of purely 

 scientific interest. One characteristic all these substances 



