492 ELECTRO-PHYSIOLOGY CHAP. 



of excitation the galvanometer was shut off, and it was ascer- 

 tained that the induction currents had not left the electrodes per- 

 ceptibly polarised. " Each excitation manifested itself by a sharp 

 decline of electromotive force. This decline is not - only relatively 

 but absolutely greater, in proportion with the approximation of 

 the coils, while at uniform distance of the coil it is much stronger 

 at the break than at the make shock. After the first, second, 

 and third excitation a positive variation (in a special case) follows 

 the negative variation ; the fourth excitation, however, weakens 

 the E.M.F. permanently, to a considerable degree, and the last 

 and most powerful break shock depresses it almost to zero, and 

 leaves it weakened to about half the original." Our own obser- 

 vations agree in the main with these conclusions, when pieces of 

 skin from any part of the body indifferently are stretched on a 

 clay block, tetanised, and led off simultaneously with the excita- 

 tion. If the frogs used (temporaria) have been kept in a cool 

 room free from frost, in vessels with a little water, the electro- 

 motive action, i.e. entering current, will regularly and invariably 

 be very powerful, with, as in the former cases, a corresponding 

 monophasic negative variation, which appears even at a compara- 

 tively low strength of current, beginning after a latent period of 

 1-2 sees., and reaching its maximum value tolerably quickly ; 

 while as after-effect of the excitation a more or less considerable 

 reinforcement of the original current of rest is usually visible, 

 which declines slowly, and never approximates to the strength 

 of the negative variation. 



Direct electrical excitation of the skin of the eel's snout, which 

 consists only of goblet cells, exhibits, according to Eeid and 

 Tolputt (83), a similar reaction to that of the frog's cloacal mucosa, 

 i.e. with weak excitation and a low development of the rest 

 current, there was a positive, with stronger excitation a negative, 

 variation of the entering current, which was always very per- 

 sistent. In the rest of the eel's skin there are, together with a 

 less number of mucous cells, other kinds of secretory elements 

 (club cells), which seem, as regards electromotive response, to give 

 an opposite reaction. According to Eeid and Tolputt (/.c.), there 

 is, with a strongly developed ingoing current and strong excitation, 

 a regular increase of the current (positive variation), while, con- 

 versely, weak excitation and low intensity of the existing E.M.F. 

 seem to favour the appearance of a negative variation. 



