426 



THE PROPERTIES OF STRIPED MUSCLE. 



the circulation as possible. An observation may be made when a con- 

 dition has been reached in which an induction current led through the skin 

 of the flank evokes a prolonged contraction instead of an instantaneous twitch. 

 Here, again, the integral curve obtained resembles the tetanic curve of injury ; 

 the proximal electrode becomes, on the whole, negative to the distal. This 

 general movement of the meniscus is interrupted by alternating upward and 

 downward movements (Fig. 241). The ascents are produced by spasms, each of 



Fig. 241. — Response to a reflex excitation — of an uninjured 

 gastrocnemius — (strychnine). 



which lasts - x ^ or T £^ of a second. The descents correspond to the intervals 

 between these spasms, and continue longer, the two together having a duration of 

 from ^jj to T y^ of a second. It is noticeable that undulations are observed in 

 each ascent, similar to those shown in Fig. 239. The larger oscillations of the 

 meniscus were long ago described by Loven, who regarded each as a response 

 to a single instantaneous stimulus emanating from the spinal cord. 1 



Phenomena which are produced by the Direct Action 

 of Voltaic Currents on Muscles. 



Polarisation of muscle. — Experimental data. — In 1883 it was 

 shown by du Bois-Keymond that, when a battery current is led for a 

 very short period from end to end through a living muscle by means 

 of terminal electrodes, the muscle being so connected by the same 

 electrodes with a galvanometer that its circuit can be closed through 

 the muscle immediately after the opening of the battery circuit, 

 currents present themselves of which the direction varies according to 

 the conditions of the experiment. These were called by du Bois- 

 Eeymond " secondary." They are also termed " polarisation " currents, 

 and the current which produces them is termed the " polarising " 

 current. If this current is of sufficient duration, the direction of the 

 secondary current is opposed to that of the polarising current. If it 

 is strong and of short duration, its direction is the same as that of the 

 polarising current. Both of these phenomena were described by du 

 Bois-Keymond, under the term secondary electromotive phenomena. 



The simplest way of demonstrating the two phenomena is indicated in the 

 diagram (Fig. 242), which shows an ordinary Pohl's reverser made of hard 

 paraffin without cross-wires, so arranged as to enable the observer to direct the 

 current of the battery (B) by the hand through the muscle. When the bridge 

 is turned over, the muscle is in the circuit of the galvanometer. For 

 investigating the phenomena, however, an automatic key or rheotome 2 must be 



1 Loven, Centralbl. f. d. med. Wissensch., Berlin, 1881, No. 7. On the subject of the 

 preceding section further details will be found in two papers published by the writer since 

 this article was in type. See Journ. Physiol., Cambridge and London, November 1898, and 

 Proc. Roy. Soc. London, 1899 (Croonian Lecture). 



2 Such an instrument is described in the Phil. Trans., London, 1888, p. 421. 



