DRUGS 335 



in later times to the building up of numberless chemical com- 

 pounds previously known only as limited products of animal or 

 vegetable life. The first example of the application of this prin- 

 ciple on the large scale was the manufacture of salicylic acid, by 

 a method discovered by Kolbe in 1874 in which phenol (carbolic 

 acid) present in coal-tar is the starting point. 



The phenol is dissolved in caustic soda producing sodium 

 phenate, C 6 H 5 ONa, and this compound, saturated with carbon 

 dioxide gas under pressure at a slightly elevated temperature, is 

 converted into sodium salicylate, C 6 H 4 (OH), COONa, from 

 which, of course, the acid is easily made. 



Since that time the number of syntheses turned to practical 

 account is very large. Two examples have already been men- 

 tioned in the two dye-stuffs, alizarin and indigo, of which the 

 history has already been given. Many other cases will be 

 referred to in the following chapters, where it will be noticed 

 that though the hydrocarbons extracted from coal-tar are the 

 fertile parents of a whole host of new substances, others are 

 actually derived from the more simple combinations of the 

 elements themselves, starting from carbon itself and bringing it 

 into a state of union with hydrogen or with the gases of the 

 atmosphere, oxygen and nitrogen. 



With this by way of preliminary we may now proceed to 

 enumerate, rather than describe, a few of the more prominent 

 among medicinal agents which are the products of the 

 chemical laboratory derived from materials of inorganic origin. 

 These are commonly referred to as synthetic drugs, to distinguish 

 them from those which, like quinine, morphine, strychnine, 

 aloin and others, are provided by nature, and which constitute the 

 active principles of plants which have long supplied active 

 remedies in the treatment of disease. These principles exist 

 ready formed in the plant, and are not in any way transformed 

 in the chemical laboratory, but are merely separated in a pure 

 state by suitable solvents or otherwise from the vegetable tissues 

 which contain them. 



Before proceeding to describe the origin of some of the most 

 modern of chemical drugs the reader may be reminded that pre- 

 vious generations have already enjoyed the use of some of the 

 agents originating in the chemical laboratory. The most familiar 

 of anesthetics, " the gas " used by every modern dentist, was 

 breathed for the first time by Sir Humphry Davy so long ago as 



