CHAP. IX.] THE CONTRACTILE TISSUES. 347 



Electrical The third form under which the actual energy 



tensions of of contracting muscle appears, is that of electrical 

 contracting disturbance. Muscles within the body, or absolutely 

 uninjured muscles, are electrically homogeneous: they 

 exhibit no current 1 . But whenever a stimulus is applied to a 

 muscle, the spot stimulated assumes a lower, or negative, potential 

 as compared with the rest of the muscle; so that if the two electrodes 

 of a galvanometer were applied to an excited and a non-excited spot 

 of muscle respectively, a current would be discovered. This func- 

 tional current increases to a maximum very rapidly and afterwards 

 disappears, but more slowly. It begins instantly on stimulation, i.e. it 

 has no latent period; and the whole phenomenon lasts about ^ 

 sec. Hence it falls entirely within the latent period of contraction. 

 It travels down excised muscles from the point of stimulation with a 

 velocity which agrees with that of the contraction-wave, namely 

 about 3 metres a second in the frog. In the normal muscles of the 

 human fore-arm the velocity has been determined to lie between 10 

 and 13 metres per sec. Like the wave of contraction, the negative 

 wave diminishes in intensity during its course along excised muscles; 

 but no such diminution has been detected in the case of muscles in 

 which the processes of restitution are active 2 . 



As is the case with the evolution of heat and mechanical 

 effect, the disturbance of electrical tension which follows stimulation 

 differs in degree according to the different conditions of stimulus, 

 irritability and tension. It increases up to a maximum as the 

 stimulus becomes more and more intense; it diminishes as exhaustion 

 approaches 3 ; it increases with the lift 4 ; and it varies directly as 

 the tension of the muscular fibres 5 . 



Rigor Mortis. 



Besides the conditions of rest and activity, there is a third 

 condition of muscular tissue with characteristic phenomena and a 

 singular bearing on the theories of muscular function, viz. the moribund 

 condition. 



After the death of the body, or after the ligature of their tributary 

 arteries, or on subjection to a certain temperature, muscles become 

 rigid. That is to say, they become shorter and thicker, and of less 



1 Hermann, "Ueber das Fehlen des Stromes in unversehrten ruhenden Muskeln." 

 Pfliiger's Archlv, Vol. in. p. 35. 



2 Bernstein, "Ueber den zeitlichen Verlauf der negativen Schwankung des Muskel- 

 stromes," Monatsber. d. Berliner Acad., 1867, p. 444. Untersuchungenu. d. Erregungs- 

 vorgang im Nerven- u. Muskelsystem. Heidelberg, 1871. Hermann, "Ueber den 

 Actionsstrom der Muskeln im lebenden Menschen." Pfliiger's Archiv, Vol. xvi. p. 410. 



3 Hermann, Handbuch der PhysioL, Bd. i. Abth. i. p. 220. 



4 Harless, Gel. Anz. d. bayr. Acad., xxxvn. p. 267, 1853; quoted by Hermann, 

 Handbuch, Vol. i. Abth. i. p. 220. 



5 S. Lamansky, "Ueber die negative Stromesscliwankung des arbeitenden Muskels." 

 Pfliiger's Arch., Vol. in. p. 202. 



