136 DEPRESSANTS TO CENTRAL NERVOUS SYSTEM 



4. Lessening the blood supply to the brain. 



5. Depression of the brain cells by drugs. 



Somnifacients are of but little if any use in veterinary medi- 

 cine as such, since we do not have to deal with insomnia of animals. 

 They are valuable, however, to relieve pain, spasm, produce mild 

 degree of anesthesia or dullness and for their other valuable side 

 actions. 



General Anesthetics are drugs which when inhaled produce un- 

 consciousness and insensibility. They have a more profound effect 

 upon the brain than the hypnotics in that they temporarily inhibit 

 the responsiveness of the cells to external stimuli and to a certain 

 extent suspend their power to recuperate. On the other hand, the 

 somnifacients inhibit the functional activity of the brain cells but 

 do not completely suspend their recuperative powers (the main 

 object of sleep) nor the power to react to external stimuli. 



General Analgesics or Anodynes are agents or remedies which 

 relieve pain. They are sometimes classified as a division of hyp- 

 notics which are especially active in relieving pain. They may 

 produce their action by directly depressing the receptive centers in 

 the brain or by preventing the passage of painful impressions 

 through the sensory nerves and spinal cord to the brain. 



Anticonvulsants are remedies which cheek excessive motor ac- 

 tivities. In cerebral con'vulsions they may act 



(1) By directly depressing the cells of the cortex of the brain. 



(2) By preventing the transmission of external stimuli to the 

 brain, through depressing the sensory side of the brain and spinal 

 cord. 



(3) By preventing the transmission of painful impulses from 

 the brain to the muscles, by depressing the motor side of the spinal 

 cord and peripheral nerves. 



GROUP OP HYPNOTICS 



The most important members of this group in their order are : 



Opium Bromides Sulpbonal 



Chloral Hydrate Chloretone Hedonal 



Cannabis Urethane Veronal 



Hyosoine Paraldehyde 



OPIUM 



Opium is the concrete juice or milky exudate obtained by incis- 

 ing the unripe capsules of Papaver somniferum, and yielding, in its 

 normal moist condition, not less than 9.5 per cent, of anhydrous 

 morphine. It is simply the dried milk-juice which exudes from en- 

 circling incisions made in the green capsules of the common poppy 

 plant of oriental countries. This plant is indigenous to Asia and 



