ACTION OF DRUGS ON THE SPINAL CORD 83 



It is impossible to find a drug whose actions are confined to 

 the cord alone, for in some degree, and with different doses, 

 the other parts of the central nervous system are affected. 

 At the same time there are drugs whose chief action is on 

 the spinal cord. By stimulation is meant an improvement in 

 the carrying out of the normal function ; the centre becomes 

 more sensitive and quicker to act. By depression is meant 

 a delay in action, and a lessening of the power to carry out 

 the normal function. 



SPINAL STIMULANTS increase the functional activity of the 

 cord. This they do by either direct excitation of the part, 

 or by the depression of those cerebral centres which control 

 the spinal centres. (See Alcohol.) The direct excitants 

 apparently act much in the same manner as mechanical 

 irritation or electricity. They seem to increase conductiv- 

 ity and lessen all resistance between the nerve-cells. Small 

 doses heighten reflex excitability ; large doses cause tetanic 

 convulsions ; whilst very large doses eventually bring about 

 depression and paralysis. Spinal stimulants include strych- 

 nine, brucine, and thebaine, as well as calabarine, caffeine, 

 absinthe, and ammonia. They are used in cases of collapse, 

 of general debility, in certain forms of paralysis, and to 

 rouse sluggish action, as of the bowels. A pure medullary 

 stimulation would be shown by quickening and deepening 

 of respiration, rise of blood pressure from vaso-motor 

 stimulation and slowing of the heart from stimulation of the 

 vagus (cardio-inhibitory) centre. 



SPINAL DEPRESSANTS comprise most of the agents which 

 depress the brain, such as the hypnotics, narcotics, and 

 anaesthetics, but in addition there are some drugs which 

 especially act on the medulla and cord. Thus hydrocyanic 

 acid, turpentine, and camphor, after more or less preliminary 

 stimulation, depress the medulla and cord. Others, such as 

 physostigmine, emetine, carbolic acid, and the antipyretics, 

 depress from the first. For practical purposes, to lessen 

 reflex action and counteract the effects of spinal stimulants 

 such as strychnine, the general narcotics and hypnotics 

 like chloral and bromides should be preferred. 



Spinal depressants are prescribed to lessen increased 

 excitability of the cord, as in tetanus, chorea, and some 

 forms of paralysis. By diminishing the conducting power 



