40 GENERAL ACTIONS OF DEUGS 



(2) Narcotics. — This term is a broad and some-what 



inclusive one. Narcotics embrace drugs which depress the 



brain and cause sleep (hypnotics or soporifics) and stupor 



(some anodynes and anaesthetics), and finally paralyze the 



respiratory and circulatory functions. The following may 



be included in this group : 



Opium Anaesthetics Cannabis Indica Stramonium 



Alcohol Chloral Belladonna Hyoscyamus 



(a) Hypnotics or Soporifics (drugs causing sleep) : 



Opium Bromides Paraldehyde Sulphonal 



-Morphine Cannabis Indica Urethrane Trional 



Chloral ( Of little importance in veterinary 



practice) 



fses.— Hypnotics are not of much value in Veterinary 

 medicine by simply promoting sleep. Their general sedative 

 and anodyne actions are utilized in relieving motor excite- 

 ment (spasms) or sensory excitement (pain). 



(b) General Ancesthetics. 



Ether Nitrous oxide Methylene bichloride 



Chloroform Ethylene dichloride Sohleich's mixture 



(Of slight value in veterinary medicine) 



Anaesthetics are agents which abolish sensation generally 

 or locally. It is thought that the general anaesthetics act 

 directly on the nerve cells. Anaesthetics — like narcotics 

 generally — first stimulate and then depress the nerve centres, 

 but depression is by far their mosb salient and useful effect. 



Anaesthetics destroy the functions of nerve centres in 

 the cerebrum and spinal cord, and so abolish pain, sensation 

 and reflex action. The law of dissolution is exemplified in: 

 their action. Anaesthesia is commonly described in three 

 stages. (1) The first or stiimdant stage is exhibited by excite- 

 ment and struggling, owing in part to fright and in part to 

 irritation of the respiratory tract by concentrated vapor, 

 'fhere are also coughing and choking in this stage, fol- 

 lowing the local irritation of the vapor on the respiratory 

 tract. There may be vomiting, and the circulation 

 and respiration are reflexly stimulated. Stimula- 

 tion now ceases, and depression of the cerebrum, 

 together with the motor, sensory and reflex spinal 



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