3 82 



THE PROPERTIES OF STRIPED MUSCLE. 



current, and loaded with 4 grms, shortens sufficiently to break the contact 

 4 -3 thousandths of a second after excitation. Under other conditions the delay 

 was somewhat greater. Ten years later the present writer was able to show, 



by the photographic 

 method, 1 that the 

 period is shorter by 

 nearly another thou- 

 sandth of a second. 

 The expansion in 

 thickness of the 

 muscular fibres of 

 the sartorius was 

 registered photo- 

 graphically with the 

 aid of the apparatus 

 for photographic 

 measurements, to be 



m. 



Fig. 213.— The induction current flows through the muscle m, 

 from d' to d, the cathode being at a. The square rod is 

 of vulcanite, the wires are of steel. 



described further on in its application to the capillary electrometer (p. 418). 

 The spring indicator shown in Fig. 213 was applied to the muscle, the move- 

 ment photographed being that of its point x. In the photograph (Fig. 214) 



the converging lines are one five-hun- 

 dredth of a second apart, the distance 

 between them corresponding to the 

 vibration period of a fork of 500 

 double vibrations per second. The 

 opening of the key by which the 

 primary circuit of the inductorium 

 is broken, is at the same time photo- 

 graphed on the plate, so that no 

 doubt can exist, either as to the time 

 after which the induction current 

 must have reached the muscle, or as 

 to the time before which the change 

 of form must have begun. The 

 photograph therefore affords incon- 

 trovertible evidence that a muscular 

 fibre begins to contract under ordi- 

 nary conditions not later than 0*0035 

 sec. after excitation. 



Fig. 214. — Facsimile of the photographic record 

 of the beginning of the contraction of the 

 sartorius. The white space is limited 



The same question has been 

 by two polar ordinates, which converge to recently discussed by Bernstein. 2 



a centre half a metre distant. In the H • tfa data of elaborate 



toothed line each tooth corresponds to & . . ., onA 



■sfo sec. Above it, the signal line in- experiments made by him m lbyu, 



dicatcs the instant of break of the primary i n which, as ill those just referred 



circuit of the induction coil (first of the t t] lt x expansion f a 

 three vertical lines). It is seen that the ' . f , , 



time which intervenes between the break muscle was registered photO- 



excitation and the response is about one graphically. He Concludes that 



^ d ^ 1 a f e *; meathedurationofatooth ' the latency period is not less 



than 0-004 second, that being the 

 shortest he was able to observe. He, however, gives no reason for 

 declining to accept the shorter estimate. 



T'nc writer of this article has shown that, as measured photographically, 



1 Bunion Sanderson, Jotim. Physiol., Cambridge and London, vol. xviii. p. 146. 



2 Arch./, d. ges. Physiol., Bonn, 1897, Bd. lxvii. S. 207. 



