THE CENTRAL NERVOUS SYSTEM 377 



EFFECT OF STRYCHNINE ON EEFLEX ACTION 



Inject with a glass pipette a few drops of 0.5 

 per cent solution of sulphate of strychnine into 

 the dorsal lymph sac of a frog the brain of which 

 has been destroyed with a seeker. 



After a few minutes, very weak afferent 

 impulses will be sufficient to call forth general 

 spasmodic reflex actions. Note that (1) the 

 strychnine reflexes are paroxysmal, (2) the mus- 

 cles fall into more or less prolonged rigidity (teta- 

 nus), and (3) the extensors overcome the flexors, 

 the limbs being strongly extended. 



The characteristic action of strychnine is evi- 

 dently not dependent on the brain. 



Destroy the spinal cord with a seeker. 



Stimulation of muscles and nerves will not 

 cause spasmodic contractions. 



Strychnine acts on the spinal cord, but not on 

 the muscles or the peripheral nerves. 



COMPLEX CO-ORDINATED EEFLEXES 



Removal of Cerebral Hemispheres. Place a 

 frog under a glass jar containing a small sponge 

 wet with ether. Be very careful not to kill the 

 frog. When insensibility is complete, place the 

 animal on a frog-board. Cut through the skin in 

 the median line of the skull, from the nose to the 



