148 



ELECTRO-PHYSIOLOGY 



CHAP. 



laid closely together, and determined the rapidity of transmission 

 to be from 2 to 7 ins. Prom this experiment of Bernstein, the 

 di< nit ion and length of an entire wave of contraction are easy to 

 determine. If a muscle of sufficient length could be procured, we 

 should be able, on exciting one end of the muscle, to follow the 

 progress of the contraction wave with the unaided eye. This is 

 prevented by the shortness of the muscle preparations practicable ; 

 but on the hypothesis that a muscle consists of physiologically 

 homogeneous fibres, we have in the curve of expansion of any 

 section an approximately correct picture of the process and dura- 

 tion of the wave of contraction, or more correctly of the altera- 

 tion in condition of the muscular elements, while the w r ave of 

 contraction is sweeping over them. The duration of the curve 

 described therefore coincides with the vibration period of the 

 wave of contraction. The rapidity of this wave being known, its 

 length also may be calculated. When the wave w (Fig. 69) is at 



the point represented in the diagram, it has already passed the 

 point of excitation p ; while at p, however, it has been trans- 

 mitted as far as /. If its duration be termed (D), its length (L), 

 and the rapidity of transmission (V), L-- VI). According to 

 Bernstein's experiments, the value of (L) is between 198 and 

 380 mm. 



In contractile substances whose conductivity of excitation has 

 been little developed, as, e.g., in Ehizopoda (Difflugia), it is at once 

 evident on exciting locally that the resulting changes are most 

 pronounced in the immediate neighbourhood of the point of 

 excitation, and become weaker in proportion as they spread by 

 conduction (Verworn, 5). On touching a pseud* >podiimi of DifHugia 

 gently with the point of a needle, the manifestations of excitation 

 (wrinkling, and extrusion of substance) are strictly localised. If the 

 stimulus is strengthened, " the phenomena extend over the entire 

 pseudopod, and arc much more rapid and vigorous after repeated 

 excitation, so that the greater part of the pseudopod, and eventually 



