NACHMANSOHN: CHEMICAL MECHANISM IN NERVES 415 



versible. The cholinesterase activity in squid nerves, under the ex- 

 perimental conditions used, could not be determined, since the season 

 was too advanced, and no squids were available. Experiments were 

 therefore carried out with the abdominal nerve cord of the lob- 

 ster. This nerve preparation has a high cholinesterase activity and 

 relatively satisfactory action potentials. The potentials recorded were 

 exclusively those of the giant axons of the cord. The transmission 

 across the synapses in the ganglia does not, therefore, enter into the 

 picture. 





Ftgurr 8. Effect of DFP on thp action potentinl of the fin nerve of sai"H. 

 DFP 0.013M. First two records (from top to bottom): before, and after, 35' in DFP. The last 

 two records : recovery after 60' and 215' in sea water. 



When the nerve is immersed in a solution of 2 mgs. of DFP per cc, 

 the action potential disappears within about 30 to 40 minutes, as in 

 the case of squid nerve. If the nerve preparation is put back into sea 

 water, the action potential reappears after some time. Nerves kept in 

 DFP for additional periods after the abolition of the action potential 

 show less complete recovery. Exposure of the nerve to DFP, for 90 

 minutes after the disappearance of the action potential, abolishes the 

 response irreversibly. 



Determinations of cholinesterase in these nerves reveal a striking 

 parallelism between the recovery of the action potential and the re- 

 appearance of cholinesterase (figure 9). The less complete the re- 



