THE MECHANISM OF CO-ORDINATED MOVEMENTS 347 



d 



THE EFFECT OF POISONS ON THE SPINAL CORD 

 The reflex functions of the spinal cord may be abolished by the same 

 drugs, such as ether chloral &c ., which abolish conductivity in a ne" 

 fibre. The central effect of these drugs is obtained with much smaller c 



LEG : 



BODY 



prostnotonic 



NECK . 

 - turning 



BODY. 



- - opisthotonic 



NECK 



retraction 



FIG. 173. Diagram by Sherrington to show influence of tetanus toxin on the 



response to excitation of the motor area of the cortex in the monkey. 

 A, normal animal. B, after poisoning with tetanus, r and / = flexion of leg 

 and arm respectively. E and e signify extension. < signifies opening of mouth ; 

 = signifies closing of mouth. 



centrations than is the case with the peripheral nerves and is the cause of 

 their anaesthetic effect. 



More interesting from the point of view of the physiologist is the action 

 of such a drug as strychnine, or the somewhat similar action of the toxin 

 formed by the tetanus bacillus. If a small dose of strychnine be injected 

 into a spinal frog, after a short period of heightened irritability the slightest 

 stimulus applied to the surface will cause spasms, which may affect every 



