CORRELATION OF THE PROPAGATION-VELOCITY OF THE 



CONTRACTION-WAVE IN MUSCLE WITH THE 



ELECTRICAL CONDUCTIVITY OF THE 



SURROUNDING MEDIUM. 



By SAMUEL ERNEST POND. 

 {From the Physiological Laboratory, Clark University, Worcester^ 



(Received for publication, May 20, 1921.) 



An attempt was made at Clark University in 1916 and 1917 to 

 test experimentally the thesis that the rate of physiological conduc- 

 tion in irritable tissues is a direct function of the electrical conduc- 

 tivity of the medium in which the tissue acts. The investigation 

 was a series of experiments with reference to the propagation- 

 velocity of the contraction-wave in the heart muscle of the river terra- 

 pin under artificial conditions. Measurements of the velocity of the 

 wave in a series of isotonic balanced salt solutions of graded activity 

 (mixtures of Ringer's solution with isotonic sugar solution) were made 

 by means of special apparatus. These preliminary results indicated 

 a direct correlation between the propagation-velocity and the elec- 

 trical conductivity, and that the ratio of velocity with respect to 

 conductivity was nearly a constant until the concentration of the 

 salts of the Ringer's solution wag reduced more than half. The 

 original apparatus has been modified and the investigation has been 

 extended during 1919 and 1921 to include the heart of the king-crab, 

 Limulus, and the sartorius of the leopard-frog, Rana pipiens. Ob- 

 servations have been made in the above solutions over an ex- 

 tended range of electrical conductivity and under nearly constant 

 conditions of oxygen tension, hydrogen ion concentration, and 

 temperature.^ 



Comparative observations upon the spreading of an excitation 

 state in irritable tissues indicate that the speed of conduction is 



^ Pond, S. E., Contraction wave in heart-muscle of River Terrapin, Thesis 

 Worcester, 1917. 



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