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



vessels to the cells, and during activity from the cells into the lumen 

 of the alveoli and through the ducts of the gland. In other words 

 there is occurring a passage of fluid through pores and minute tubes, 

 and it may well be that the observed differences of potential are 

 caused partly if not entirely by this movement. We shall however 

 immediately show cause against the adoption of this theory. 



Cat. — The current of rest in the cat, when the gland is led 

 off in the same manner as in the dog, is as we have already men- 

 tioned more variable in its sign ; the surface of the gland being some- 

 times negative but much more frequently positive to the hilus. That 

 is to say the current of rest is usually in the opposite direction to 

 that which is noticed in the dog. Out of twenty experiments, in fifteen 

 the surface of the gland was positive to the hilus, in three negative, 

 in one the gland surface was at first negative and subsequently be- 

 came positive, and in one it was at first positive and subsequently 

 became negative. Now although we would not draw too positive 

 conclusions from the average results of a few experiments it would 

 nevertheless appear that the resting current of the cat's submaxillary 

 is normally in the opposite direction to that of the same gland in the 

 dog. There are many possible sources of error, some of which have 

 been mentioned above, which might tend to vitiate the above con- 

 clusion, but we are on the whole inclined to adopt it as correct. 



Now presumably the conditions as to the flow of fluid in the cat's 

 submaxillary are similar to those that obtain in the same gland of 

 the dog, but what may be called the truly secretory processes in the 

 two glands are different and we find that the distribution of potential 

 is also different in the two cases. We conclude therefore that the 

 differences of potential which cause the current of rest are largely 

 due to the physiological processes which are going on within the 

 gland- cells. 



On the other hand we would by no means affirm that the passage 

 of fluid through the vessels and ducts of the gland, the unavoidable 

 injury to the gland and its surroundings and the fact that the elec- 

 trodes themselves rarely remain equipotential for a long period, do 

 not each of them exert an influence on the amount and sign of the 

 current of rest. On the contrary we believe that most, and possibly 



