650 



PRINCIPLES OF GENERAL PHYSIOLOGY 



Charges on the surface of membranes themselves, dealt with by Mines (1912, 1), 

 and discussed in relation to those of colloids on pages 89-91 of the present work, 

 are difficult to bring into relation with the electromotive phenomena of cells. Of 

 course, if a membrane adsorbs preferentially one ion of an electrolyte with 

 which it is in contact, owing to the greater decrease of surface energy by this 

 ion than by the opposite one, the membrane will obtain the charge of the 

 adsorbed ions. Whether this would show itself in the form of a potential 

 difference between the two sides of the membrane seems doubtful. 



Baur (1913), however, 

 has described what he calls 

 a model of the electric fish, 

 in which such charges . on 

 membranes appear to play a 

 part. If a mixture of 

 "turkey red oil" with three 

 parts of acetylene tetra- 

 chloride, be shaken with 

 water and allowed to stand, 

 a separation into an oily 

 phase and a watery phase 

 takes place. The lipoid 

 phase is said to contain some 

 water, sodium sulpho-ricin- 

 oleate, sodium sulphate, 

 castor oil, and acetylene 

 tetra-chloride. This is satur- 

 ated with mercurous sulphate 

 and electrodes made by con- 

 tact with mercury. Two 

 such electrodes in potassium 

 sulphate solution have, of 

 course, equal and opposite potential differences : 



Hg | lipoid | K 2 SO 4 | lipoid | Hg, 



so that the combination has no electromotive force. If, however, to the potassium 

 sulphate solution on the one side an electrolyte with a strongly adsorbed cation, 

 such as quinine sulphate, is added, this electrode becomes positive to the other. 

 If the sodium salt of fluorescein, with strongly adsorbed anion, is added, the 

 electrode becomes negative. Thus, with quinine sulphate on one side and 

 fluorescein on the other, an electromotive force of 0'36 volt was obtained. The 

 system is somewhat complex, probably unnecessarily so, and may, perhaps, be 

 equally explicable on the basis of solubility of one ion only in the lipoid phase. 

 The result would be the same. 



We may now proceed to refer briefly to some actual cases where electromotive 

 phenomena have been found to accompany the activity of cells. 



FIG. 206. DIPHASIC ELECTRICAL CHANGE IN 

 GASTROCNEMIUS MUSCLE OF THE FROG. 



Led off to string galvanometer from two uninjured places on the 



surface of the muscle. 

 Sciatic nerve stimulated by a single shock at E on the signal line S. 



M, The electro-myogram. 



One scale division of abscissae is equivalent to 0'002 sec. 



One scale division of ordinates is 7 millivolts. 



(Einthoven, 1913, p. 67.) 



EXAMPLES 



Nerve. The electrical response in nerve has been discussed above (page 379). 

 Fig. 101 shows its character in the olfactory nerve of the pike. 



An important use of the fact has been made in several cases already referred 

 to. The measurements of the time relations of the kpee-jerk by Jolly (page 475), 

 the impulses arising in the vagus nerve by distension and collapse of the lung by 

 Einthoven (see Fig. 106, page 386), and the impulses in the depressor fibres caused 

 by increase of pressure in the aorta, also by Einthoven (in Fig. 106), may be 

 mentioned. 



Keith Lucas (1912) examines the evidence that has been brought forward 

 to show that the process gf excitation is not necessarily accompanied by an 

 electrical change, and comes to the conclusion (p. 507) that none is free from 



