1906.] The Action of Ancesthetics on Living Tissues. 161 



In the Experiments 502 to 506 inclusive, moist air containing about 

 16 per cent, of CHC1 3 vapour delivered from the apparatus previously 

 described (Part I)* was applied first to the part of the chamber containing 

 electrode B, which touched the inner surface, and secondly to electrode A, 

 which touched the outer surface, the electrode not receiving CHCI3 being 

 ventilated with moist air. The figures plotted out in fig. 2 are the successive 

 readings of the potentiometer balancing the E.M.F. from the skin, as in the 

 previous experiments on nerve.f 



It will be seen that CHCI3 to B produces a minimal effect, J while CHCI3 

 to A causes an immediate and very rapid fall to the zero line. In Experi- 

 ments 500 and 501 (fig. 3) the order was reversed, CHCI3 to A produced 

 a fall of potential exactly as in fig. 2, CHC1 3 to B having again but a very 

 slight action. The conclusion is therefore — 



(i) CHCI3 to the outer surface of the skin abolishes the current. 



(ii) CHCI3 to the inner surface of the skin has no action (neglecting the 

 minimal effect noted above). Erom these conclusions follows another — 



(iii) The apparatus giving the current is placed at or very near the outer 

 surface. 



Further inferences can be drawn ; they are considered later. 



Series II. 



In Experiments 507 and 508 advantage was taken of the third electrode C 

 which touched the outer surface opposite the electrode B, and measure- 

 ments were taken by means of the ABC key of the potential between 

 A and B, B and C, and A + C (in parallel) and B. The intervals between 

 successive observations of the same pair of electrodes were about one minute, 

 and the readings were in the order given, so that the readings for BC and 

 (A + C) B are in each case a little later than those of AB. In both 

 experiments all three readings showed the gradually lessening increase 

 characteristic of a normal preparation under the conditions of experiment. 

 CHCI3 was then applied to the chamber containing electrodes BC. 



* Loc. cit., p. 271. 



t The figures have been corrected for electrode current ; the error of reading is about 

 ± 0-0001 volt. The potentiometer error is rather more, but as this is constant for all the 

 experiments, no correction has been applied. 



% This is probably due in part to a slight escape of CHC1 3 vapour to A, in part also 

 because, although the outer surface has a high resistance (vide infra), this is not infinite. 



