GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 153 



arm, found the rate of spread of the active process by the voluntary contraction 

 of human muscle to be from 10 to 13 meters per second. Du Bois-Reymoud 

 dipped a finger of each hand into fluid contained in cups connected with a 

 galvanometer. If the muscles of one arm were vigorously contracted, a 

 deflection of the magnet was seen. This was probably due to electric currents 

 from the glands of the skin and not from the contracting muscles. 



Relation of the Negative Variation Current to the Contraction. — Bernstein 

 observed the negative variation of the demarcation current of the muscle 

 almost at the instant that the muscle was excited and before the contraction 

 began to be recorded — i. c, during the mechanical latent period of the muscle 

 — and concluded that it is associated with the excitation rather than the con- 

 traction process. This view is supported by others, 1 who find that the 

 highest point of the negative change is generally passed before the contrac- 

 tion shows itself. 



On the other hand, it is reported that the negative state may continue 

 throughout the contraction. Sanderson and Page 2 saw the diphasic change 

 which accompanies the beat of the heart to last throughout the systole ; and 

 Lee 3 found the diphasic change which occurs when a skeletal muscle of 

 a frog is excited by a single stimulus, to continue as long as the muscle re- 

 mains active, including the period of relaxation ; in some cases it lasted from 

 0.05 to 0.06 second. Sanderson, as we have seen (see Fig. 6ti), tetanized 

 injured skeletal muscles of the frog, and found not only a series of negative 

 variations corresponding to the contraction processes which resulted from the 

 separate excitations, but also a continuous negative variation, the diminutional 

 effect, which developed comparatively slowly and lasted after the irritant 

 had ceased to act. 



Still other observers, who claim that the electrical state of the muscle is 

 closely related to the contraction process, find sometimes a negative and 

 sometimes a positive change, according as the contractions are isometric or 

 isotonic. 



A further consideration of this subject would be out of place here. Suf- 

 fice it to say that there can be no doubt that the change which occurs in 

 muscle substance when it is excited is associated with a change in its elec- 

 trical condition ; whether the subsequent activity of the muscle protoplasm, 

 manifested in the change of form, has also an electrical change associated 

 with it, must be left an open question. 



4. Currents of Action in Nerves. — In general, the fads which have 

 been stated with regard to the current of action in muscles apply to nerves. 

 When a normal nerve is excited a negative change is forthwith developed at 

 the stimulated point and passes thence in both directions along the nerve at 

 the same rate as the nerve-impulse. This change is diphasic, first the part 

 excited and latin* distant parts showing the negative change. If the nerve 



1 Jensen : Pfluger'a Archiv, L899, Bd. lx.wii. S. 107. 

 1 Journal of Physiology, l s 7'.», vol. ii. p. 396. 



8 Archir fur Anatomic mid Plti/.<it>l<>(fie, 1SS7, S. 'J04. 



