The Characteristic of Nerxe. 



211 



The muscular contraction was watched for, and occasionally recorded 

 in the usual way. 



As regards the human subject, the circuit was as before, a Stohrer's 

 battery up to 60 volts being used to charge the condenser. One large 

 electrode (the "indifferent" electrode) was strapped to the abdomen; 

 a second small electrode (the " testing " electrode) was fixed over an 

 accessible nerve, such as the ulnar, median, or peroneal. 



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To illustrate rate of energy discharge and approximate gradients when the 

 constant has not less than two digits nor more than three digits. The shaded 

 area indicates range within which the nerve characteristic must have fallen. 



The procedure was of three types : — (1) To take a series of com- 

 binations between voltage and capacity, so as to deliver constant energy 

 at various rates ; (2) to take a series of voltages and find for each 

 voltage the smallest capacity at which contraction was visible ; (3) to 

 take a series of capacities and find for each capacity the smallest voltage 

 at which contraction was visible. 



The first plan has the considerable advantage of permitting the use 

 of a myograph. It is chiefly serviceable for the purpose of a pre- 

 liminary orientation, i.e., when it is desired to find quickly the range 

 at which the characteristic is to be looked for. Having obtained a 

 minimal effect with any given voltage and capacity, the next test is to 

 be made with half the voltage and four times the capacity, i.e., with 

 the same energy as before, but with that energy falling by a curve 

 with a constant equal to one-eighth of the constant of the previous case. 

 If the effect is manifestly greater, the voltage is again to be halved and 

 the capacity quadrupled from the starting point of a new minimal 

 effect. If, on the other hand, after the first step in reduction of the 



