ELECTRICAL CHANGES IN TISSUES 



651 



objection. We are, at present, entitled to hold the view that one is an aspect 

 of the other. 



Muscle. This also has been already 

 discussed (page 539). Fig. 205 is from 

 a photograph by Keith Lucas of the 

 diphasic response in the sartorius 

 muscle, and Fig. 206 is one by 

 Einthoven, with the string galvano- 

 meter. We have shown how it 

 is to be explained on the basis of 

 the theory of the origin of potential 

 difference given in previous pages of 

 the present chapter. 



In muscle, just as in nerve, it 

 appears that the electrical change is 

 connected with the process of excita- 

 tion ; the excitation process is possible 

 in muscle without the contraction pro- 

 cess (page 539). The latter is a result 

 of the excitation process, but may be 

 unable to follow it. Fig. 172 (page 

 539) (middle curve) shows that, in the 

 absence of calcium, the electrical 

 change in the heart muscle takes 

 place without any mechanical change. 

 The significance of this fact has been 

 pointed out above (page 398). 



As to the precise location of the mem- 

 branes concerned, both in nerve and in 

 muscle, we must not forget the possibility 

 that such polarised surfaces may occur, not 

 only at the cell membrane on the outside 

 of the cell, but at phase boundaries within 

 it. But much more knowledge is required 

 of the cell mechanisms. 



The way in which the " demarca- 

 tion " current, or current of injury, is 

 to be explained has been described 

 previously. A further word of ex- 

 planation may be added here. If an 

 uninjured cell, at rest, is led off from 

 any two points on its outer surface, 

 it is clear that they will be equi- 

 potential, since we are only dealing 

 with the outer component of the 

 double layer. If we could place one 

 electrode inside the cell, we should 

 obtain the potential difference between 

 the two components of the layer, as 

 in my experiments with Congo-red 

 (1911, 2). This is, in fact, what we 

 do when we cut through or injure 

 a cell in contact with normal cells, 

 leading off from the outer surface of 

 the normal cells and from the injured 

 cells. This latter contact is, in effect, 

 the same as the interior of the cell. 



We saw above (page 393) how the disappearance of this potential difference 

 on stimulation (" negative variation ") is explained by the disappearance of the 

 state of polarisation in the normal cells, owing to the membrane becoming 



Fio. 207. ELECTRICAL CHANGES ACCOMPANYING 



THE PASSAGE OF A WAVE OF CONTRACTION 



ALONG THE URETER. To be read from left 

 to right. 



A, Print from photograph given by string galvanometer. 



Two complete waves. 



Distance between electrodes 50 mm. 

 V, Electrode at which the wave first arrives becomes 



positive. 



H,, The chief negative wave. 

 T 2 , Negativity of distant electrode. 

 ff, Positivity of distant electrode. 



B, Shows appearance of original photograph. One com- 



plete wave only is seen. The above four components 

 are obvious. Time in seconds. 



C, A wave which disappeared before reaching the second 



electrode, so that the electrical change under the 

 first electrode only is shown, namely, the components 

 V and //,. Time in fifths of seconds. 



(Orbeli and Briicke.) 



Note that the figures are reproduced as sent me by Dr 

 Orbeli. Those in the published paper are incorrectly 

 given. 



