444 THE PROPERTIES OF STRIPED MUSCLE. 



muscle current of the ventricle, coincident with relaxation. Sub- 

 sequently (1872), Donders 1 confirmed these observations, and, by skilful 

 application of the graphic method, determined the time relations of the 

 phenomena. The subject was next taken up by Engelmann 2 in 1873, 

 who then established that, when at rest, " the surface of the uninjured 

 heart exhibits no difference of electric tension " (i.e. is equipotential), 

 and by means of the galvanometer and rheotome, investigated the 

 duration and time-relations of the excitatory change. He found that, 

 in general, when the ventricle was excited at a point near to one of the 

 leading-off electrodes and remote from the other, " the nearer of the two 

 became on excitation first negative, then positive to the more remote." 

 As the result was the same whether the contacts were at base and 

 apex, or on opposite sides of the ventricle, it was concluded that every 

 excited part becomes momentarily " negativelectromotorisch wirksam" 

 and that this negativity " is propagated from the seat of excitation in 

 all directions" 3 (loc. tit., p. 73). Such a diphasic effect ^ was termed 

 by Engelmann a Doppekchwankung. When the negativity of the 

 nearer contact culminated at 016 second after excitation, it was 

 succeeded 014 second later by relative positivity (positive Schwan- 

 famg), i.e. negativity of the further contact, and had completely 

 subsided half a second after excitation. Considering that each phase 

 was of very short duration, and that the wave of excitation may 

 reach the second electrode before it has culminated at the first, he con- 

 cluded that the whole period occupied by the electrical disturbance is 

 not more than y 4 ^ of a second. 



In 1879 I made, in conjunction with Mr. Page, 4 an extensive series 

 of experiments, in which the electromotive phenomena of the response 

 were investigated with the galvanometer and rheotome, and also with 

 the electrometer, the photographic method being used for recording (see 

 p. 418). For both series of observations the preparation chiefly used 

 was the " Stannius heart," i.e. one brought into a state of atonic quies- 

 cence by a ligature applied between the sinus and the auricle. 



The rheotome observations showed that in such a heart, at 15° C, 

 the variation evoked by excitation of the auricle consists of two phases, 

 separated from one another by a period during which the surface of the 

 ventricle is equipotential. The first lasts about 0'05 second, the 

 equipotential period 1-3 second. The duration of the second phase 

 exceeds that of the first, but its difference of potential is relatively very 

 inconsiderable. The duration of the ventricular systole was recorded 

 graphically at the same time, and found to be about 11 second, so that 

 it did not last quite as long as the interval between the two phases. 

 There was no difficulty in explaining the first phase of the variation in 

 accordance with the principles already laid down by Engelmann ; but 

 the existence of a second phase, separated from the other by a long 

 period of equipotentiality, was a new fact which neither he nor anyone 

 else excepting Kolliker and Miiller had observed, for Engelmann applied 

 the term Doppelschwankung exclusively to the initial period of about a 

 third of a second, during which (in the normal beat) the base becomes 

 first negative, then positive, to the apex. It seemed probable from the 



1 Donders, Onderszoek. ged. in h. physiol. Lab. d. Utrecht. Hoogcsch., 1872, Bd. i. S. 2f»6. 



2 Engelmann, ibid., Bd. iii. S. 806. 



3 Arch.f. d. ges. Physiol., Bonn, 1874, Bd. xvii. S. 68. 



4 Jour n. Physiol., Cambridge and London, vol. ii. p. 384. 



