118 W. M. Bayliss and J. R. Bradford, 



tive but subsequently became negative, and in one case it was at 

 first negative but subsequently became positive. In all the other cases 

 the outer surface was negative to the . hilus throughout the whole 

 experiment. 



A variety of structures, especially muscles, are unavoidably injured 

 in the preparation, and some of these are in the region of the elect- 

 rodes. It is more than probable that this is one reason for the fact 

 that the current of rest varies in different cases. But that injury is 

 not the sole cause of this variability is seen from the circumstance that 

 in the cat, where a corresponding amount of injury is done to similar 

 parts, the current of rest is usually opposite in sign to that which 

 normally obtains in the dog. This seems to show that the nature of 

 the gland largely modifies the electrical condition during rest. 



The electromotive force of the current of rest varies within wide 

 limits, both in different animals and in the same animal at different 

 times. In the former case it may vary from the Vsoo volt to the 

 Vio volt. No doubt these large variations are due in great part to the 

 variable character of the injury inflicted by the operation, but we 

 think that the changes in the activity of the gland also participate 

 in producing them, and in support of this we would mention the 

 following facts : — 1) It is often found that at the beginning of an ex- 

 periment the current of rest is undergoing constant changes, so that 

 there is considerable difficulty in compensating it. After a few ex- 

 citations of the chorda or sympathetic, the resting current, although 

 as will be immediately mentioned, it may be either slowly increasing 

 or slowly diminishing in amount, yet no longer exhibits the great 

 fluctuations which existed prior to the excitation. This seems to show 

 that the changes produced in the gland by nerve - excitation not only 

 produce sudden changes of potential (the excitatory changes to be 

 presently described), but also modify the processes going on in the 

 intervals of excitation. 2) Changes in the current of rest are brought 

 about by excitation of the gland -nerves (apart from the excitatory 

 variation described below) either of a purely temporary, or of a more per- 

 manent character. Thus stimulation of the chorda tends to produce a tem- 

 porary diminution in the current of rest, and stimulation of the sympathe- 

 tic, an increase; that is to say, it is followed in both cases by an after 



