316 INOBGANIC AGENTS 



In small medicinal doses the circulation is not influenced 

 materially, but in poisoning the pulse at first is accelerated 

 and then becomes slow, weak and irregular, and the heart 

 is arrested in diastole. 



Nervous System— The salient action of chloral is exerted 

 upon the brain and cord. Like other narcotics, the depress- 

 ing effect may be preceded by a transient and unimportant 

 excitation of the brain and cord ; but this commonly passes 

 unnoticed, and the prominent action of chloral consists, in 

 ordinary doses, in depressing the sensory and motor 

 centres of the brain, and in larger doses, the spinal 

 reflex activity and the motor tract of the cord. Mo- 

 derate therapeutic doses cause, therefore, dulness an^ 

 sleepiness (with contracted pupils) in the lower animals, 

 while doses approaching the toxic point produce insensi- 

 bility, coma, paralysis of the inferior cornua, with loss of 

 reflex action and muscular power, so that the animal 

 falls; paraplegia, dilated pupils and anaesthesia. These 

 symptoms may occur and be followed bj recovery. The 

 anaesthesia is of spinal origin. Neither the sensory nerves, 

 motor nerves, nor muscles are affected except in the later 

 stages of poisoning. 



Insensibility to pain is said, by Brunton, to follow the 

 action of chloral upon the gray matter of the cord, by pre- 

 venting the transmission of painful sensations through this 

 tract. It is uncertain whether chloral acts as an hypnotic by 

 its direct depressing influence upon the brain tissue, or by ' 

 inducing cerebral anaemia in causing the blood to be with- 

 drawn from the cerebrum into the dilated peripheral arte- 

 rioles. 



Bespiration. — The respiration is not interfered with by 

 moderate medicinal doses of chloral, but toxic quantities 

 depress and paralyze the respiratory centre. The respira- 

 tory movements become deep, regular, accelerated (26) and 

 full, with large therapeutic doses, but with toxic doses^ 

 slow, irregular and shallow. Death occurs more commonly 

 from arrest of respiration, yet primary heart failure, or both 

 combined, may lead to a fatal result. 



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