DRUGS WHICH ACT UPON THE NEEVOUS SYSTEM 



479 



ANAESTHETICS AND ANODYNES 



These are certain drugs which so blunt the senses that little or no pain 

 results from causes which in their absence induce it. They have a local or 

 general effect according to the mode of application. Some, as cocaine, 

 veratrium, and aconite, when applied to the skin, deprive the nerves of the 

 part of sensation, so that they may be cut or even burned without causing 

 pain at the time. Tnis action is called 

 local anaesthesia, and the agent em- 

 ployed, an anaesthetic. 



Ether spray or other applications 

 producing intense cold by rapid evapo- 

 ration have also the effect of producing 

 insensibility, but experience has proved 

 that this method of producing anaes- 

 thesia is sometimes attended with after 

 consequences of a very undesirable 

 character. Evaporating lotions, com- 

 posed largely of the cheaper forms of 

 spirit, are frequently prescribed to 

 reduce pain in inflamed limbs, tendons, 

 and joints, their effect being the result 

 of the cold induced in the part. The 

 application of ice and ice -water is 

 attended with similar results. 



General Anaesthesia is produced 



by the inhalation of drugs such as 



IIP i , i i , i 1, Capsule showing Turkish method of incision to get 



chloroform and ether, and the same opium . 2> See d. 3, Section of seed. 



end may be attained by introducing 



them into the blood either through the stomach or by subcutaneous injec- 

 tion. These agents, by acting on the brain and spinal cord, induce sleep 

 and insensibility to outward impressions and inward pain, and in the 

 latter connection rank with that class of agents termed anodynes. Given 

 in certain doses, they soothe the whole body and reduce the activity of 

 different organs; then they are classed as sedatives. Since their effect is 

 also to relieve spasm, they are known as anti-spasmodics. 



Opium and its Alkaloids. At the head of the- list stands opium, 

 where Percival, the father of veterinary medicine, placed it, and described it 

 as " the sheet anchor of the veterinarian ". Its method of production need 

 riot be described here. 



Fig. 432. Opium Poppy (Papaver tomniftrwn) 



