702 ALKALOIDS ABE AMMONIA DERIVATIVES 



result from the metamorphosis of albuminoid plant consti- 

 tuents. They constitute the active principles of vegetable 

 drugs, and are generally powerful poisons or active medicines. 

 Those chiefly used are morphine, atropine, quinine, cocaine, 

 physostigmine, pilocarpine, and strychnine. 



Most alkaloids contain carbon, hydrogen, and oxygen, 

 and all contain nitrogen. But although the molecule may 

 contain twenty or thirty carbon or hydrogen atoms, there 

 are seldom more than two atoms of nitrogen. They are 

 generally crystallisable solids. Three of the natural alka- 

 loids, conine, nicotine, and sparteine, contain, however, no 

 oxygen, and are volatile liquids. Alkaloids are ammonia 

 derivatives, but their sparing solubility in water renders it 

 unlikely that they are ammonium bases ; their not subliming 

 without some decomposition distinguishes them from the 

 amines ; their feebly basic character and other properties 

 more nearly ally them with the amides. They may other- 

 wise be defined as substituted ammonias, capable of forming 

 salts by direct addition of acids. Many are closely related 

 to pyridine, and a few may be prepared synthetically from 

 pyridine bases. Most are soluble in alcohol, ether, benzine, 

 and carbon disulphide, and usually in chloroform, which 

 does not, however, dissolve morphine. Most are sparingly 

 soluble in water. Alkaloids readily unite with acids, 

 forming salts, soluble in water ; and with radicles such 

 as ethyl and methyl, forming combinations which greatly 

 modify their actions, as is strikingly illustrated in the differ- 

 ence between conine and methyl-conine. Their chemical 

 composition affords no clue to their physiological action. 

 Those of diverse composition have sometimes similar actions ; 

 those apparently of like composition differ in their actions. 

 Between the anodyne soporific morphine, and the emetic 

 apomorphine, the formulae show a difference of only the 

 elements of water. Plants of the same genus usually yield 

 the same or similar alkaloids ; thus the atropaceae yield 

 atropine, the strychnos strychnine. Alkaloids are often 

 associated in plants with some special acid, in combination 

 with which, or with a diluted acid added to the plant 

 juices, they are dissolved out, usually by water, and from 

 such solution the alkaloid may be precipitated by ammonia. 



