.404 VEGETABLE DEUGS 



of the spinal cord from the brain in animals shows conclu- 

 sively that strychnine convulsions are of spinal origin. 



Ingenious experiments furthermore indicate that the 

 tract in the spinal cord — which is acted upon to cause in- 

 creased motor responses to sensory stimuli — is situated be- 

 tween the entrance of the sensory roots into the cord and 

 the motor cells of the inferior cornua. Or, more precisely, 

 the seat of strychnine action appears to be immediately 

 adjoining the afferent side of the inferior cornual cells. 



Increased reflex excitability produced by strychnine has 

 been heretofore attributed to the direct stimulating action 

 of the drug on the motor tract of the cord. This is appar- 

 ently not the case, for, when a solution of strychnine is ap- 

 plied to the cord at the level of the cells controlling the fore- 

 legs, and the forelegs are irritated, there is increased con- 

 traction 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. The action of strychnine on 

 the cord is thought to be indirect. 



That in some way it removes the natural resistance to 

 the passage of afferent impulses to the motor cells and there- 

 fore a greater force remains to be expended on the motor 

 cells (Cushny). To put it more briefly, strychnine increases 

 the conductivity of the cord for sensory impulses. 



In fatal strychnine poisoning general paralysis ensues 

 through depression of the spinal sensory aiid motor centres. 

 This may be immediate after enormous doses, with absence 

 of convulsions ; or appear at the end of fatal poisoning. The 

 mooter 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 af- 

 ferent nerves -are unaffected by strychnine. 



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