INTRODUCTION. 13 



Analgesics or Anodynes are agents which re- 

 lieve pain. This is accomplished in two ways— 

 either by impairing the conductivity of the sensory 

 nerve fibres, or by depression of the cerebral centres 

 of perception and sensation. Opium acts in both 

 ways at the same time, and is therefore the most 

 powerful member of this group. 



Anodynes are divided into Geneeal Anodynes 

 and Local Anodynes. 



The General Anodynes are taten internally and 

 so act upon the entire organism, as opium, bella- 

 donna, henbane, aconite, ether, and chloroform. 



Local Anodynes affect the part to which they are 

 applied, generally by direct action upon the nerve 

 endings in the skin and sometimes by reducing the 

 local circulation. These include opium, belladonna, 

 carbolic acid, cocaine, veratrine, aconite, chloroform, 

 etc. 



ANiESTHETics are agents which temporarily de- 

 stroy sensation. 



The General Ancesthetics are volatile substances 

 which when inhaled produce more or less complete 

 unconsciousness and loss of sensation (anaesthesia), 

 and also decreased motor power. 



Local Ancesthetics act like the local anodynes but 

 destroy sensation temporarily, while the local ano- 

 dynes only lessen sensation temporarily — that is, at 

 the part applied. 



Chief General Ancesthetics : Ether, methylic 

 ether, chloroform, nitrous oxide, methylene and ethy- 

 lene bichlorides. 



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