BRINK AND OTHERS: CHEMICAL EXCITATION OF NERVE 475 



choline per cc, during continuous perfusion with solutions containing no 

 inhibitor of cholinesterase. When the threshold for a cell is exceeded, 

 it discharges impulses with a regular rhythm, and for extended periods 

 that we have observed to be as long as an hour. The frequency of this 



B 



Figure 16. Impulses discharged from a single sympathetic ganglion cell in response to acetyl- 

 choline in concentrations of A:25; B :50 ; C:100 micrograms per cc. Cat's stellate ganglion per- 

 fused with a modified Ringer's fluid containing acet.\lcholine, but no inhibitor of cholinesterase. 

 Impulses recorded from a fine strand of the postganglionic nerve. Time in seconds. 



discharge increases with increased concentrations of acetylcholine (fig- 

 ure 16) . Finally, at concentrations of about 200 micrograms per cc, 

 the excitatory action ceases, the discharge of impulses is arrested, and 

 the ganglion cells cannot be stimulated by volleys of preganglionic 

 impulses. 



The response of nerve to chemical excitants depends upon the totality 

 of environmental agents. This has been emphasized before. It is a 

 fact that is illustrated by the effects of the combined action of acetyl- 



