STRYCHNINE 399 



the brain in animals shows conclusively that strychnine convulsions are 

 of spinal origin. 



Ingenious experiments furthermore indicate that the tract in the 

 spinal cord — ^which is acted upon to cause increased motor responses to 

 sensory stimuli — is situated between the entrance of the sensory roots 

 into the cord and the motor cells of the inferior cornua. The receptive 

 neurons (connecting the motor and sensory spinal neurons) appear to 

 be directly influenced by strychnine so that nerve impulses pass through 

 unhindered. 



Increased reflex excitability produced by strychnine has been here- 

 tofore attributed to the direct stimulating action of the drug on the 

 motor tract of the cord. This is apparently not the case, for, when a 

 solution of strychnine is applied to the cord at the level of the cells con- 

 trolling the forelegs, and the forelegs are irritated, there is increased 

 contraction of the hind as well as the fore limbs. The motor cells of 

 the hind limbs, in this experiment, are not directly acted upon by 

 strychnine at all. 



According to Cushny, strychnine removes the natural resistance to 

 the passage of afferent impulses to the motor cells and therefore a greater 

 force remains to be expended on the motor cells. To put it more briefly, 

 strychnine increases the conductivity of the cord for sensory impulses, 

 both across and up and down the cord. As muscle tone depends upon 

 afferent stimuli strychnine is supreme as a tonic. Metabolism is stimu- 

 lated through the greater glandular and muscular activity caused by the 

 increased irritability of the central nervous system. 



In fatal strychnine poisoning general paralysis ensues through de- 

 pression of the spinal sensory and motor centres. This may be im- 

 mediate after enormous doses, with absence of convulsions ; or appear at 

 the end of fatal poisoning. The motor nerve endings are also paralyzed 

 but this is secondary in mammals to the more important paralysis of the 

 motor and sensory spinal centres. The voluntary muscles and afferent 

 nerves are not directly affected by strychnine. 



Respiration. — Strychnine has hitherto been regarded as chief among 

 respiratory stimulants but recently noted clinicians have found little 

 effect from it on the respiration in large therapeutic doses. In pathologic 

 conditions with exhaustion it is likely the action, as upon other spinal 

 centres, is indirect, L e., the respiratory centres are made to respond 

 more forcibly to sensory stimuli. 



Organs of Special Sense. — The sense of sight, smell, hearing and 

 touch is rendered more acute by strychnine. 



Elimination. — Strychnine escapes to some extent unchanged, in the 

 urine. It appears within half an hour of ingestion and a part is delayed 

 in the tissues and may be discovered in the urine from 3 to 8 days 

 thereafter. The greater part of strychnine is probably oxidized in the 

 body. The drug is not cumulative, in the sense of producing sudden and 

 violent action following its continual use. in increasing doses. A toler- 

 ance for it can be acquired In man and with difiiculty in dogs. 



Administration. — For tonic purposes, strychnine may be given to 



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