22 CLASSIFICATIONS OF MEDICINES 



corrosive substances as caustic soda and sulphuric acid, 

 entering into chemical combination, produce a neutral, com- 

 paratively mild saline. Organic, like inorganic bases, are 

 notably modified by the acid radicles with which they 

 unite. Thus, amyl-hydride is an anaesthetic ; when oxygen 

 is introduced, as in amyl-alcohol, or amyl-acetate, spasm is 

 added to the anaesthesia ; amyl-iodide notably increases 

 secretion, while amyl-nitrite lessens arterial pressure. It 

 is hence evident that the action of a compound medicine 

 cannot be inferred from a knowledge of the action of the 

 substances that combine to form it. On the contrary, a 

 compound substance exerts special actions of its own, these 

 depending on the proportion of its components, and upon 

 its own physical qualities. 



Very important investigations have been made by 

 Crum Brown, Fraser, Schroff and Jolyet, in artificially 

 modifying the chemical constitution, and thus changing the 

 physiological actions of drugs. When strychnine, brucine 

 and thebaine, which act upon the spinal cord as powerful 

 convulsants, are converted by addition of methyl into 

 methyl-strychnine, methyl-brucine and methyl-thebaine, 

 they act upon the ends of motor nerves as paralysants. 

 Indeed, methyl, when combined with other alkaloids, as 

 quinine, morphine, atropine and codeine, renders these also 

 powerful paralysers of motor nerves. 



The study of the natural orders of plants affords some 

 general information as to their physiological actions. Thus, 

 the Ranunculaceee furnish many acrid irritants, such as 

 aconite, podophyllum and stavesacre. The Solanaceae yield 

 narcotics, such as tobacco and dulcamara ; while the sub- 

 order, Atropacese, are paralysers of nerve terminals. The 

 seeds of many Umbelliferse yield carminative volatile oils. 

 These general botanical characters do not, however, afford 

 sufficient data for the accurate classification of drugs. 

 Edible as well as poisonous plants occur in many natural 

 orders. Plants of different orders and genera sometimes 

 closely resemble each other, while plants of the same genus 

 may have very different properties. Thus, one species of 

 Strychnos yields strychnine, which stimulates the motor 

 centres of the spinal cord, inducing tetanic convulsions, 



