BRINK AND OTHERS: CHEMICAL EXCITATION OF NERVE 459 

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FiGTJRB 1. Threshold of giant axon of Squid in isotonic solutions containing various concentra- 

 tions of CaCh. Threshold (rheobase) as per cent of threshold of nerve in Woods Hole sea 

 water. Concentration in millLmoles per liter. The arrow indicates concentration at which spon- 

 taneous activity began. 



FiGDEE 2. Threshold of a fibers of sciatic nerve of frog with various concentrations (millimoles 

 per liter) of CaCh in bathing fluid. Threshold as per cent of rheobase of nerve m reference 

 aolution described in text. 



