SAMUEL ERNEST POND 809 



tact with an electrolyte solution. "^ This hypothesis "assumes that 

 the electromotor properties of the protoplasmic surface-film are de- 

 termined by conditions which are fundamentally similar to those 

 governing the electromotor phenomena at metallic surfaces. "^ With 

 irritable tissues, just as with metallic elements under certain con- 

 ditions, e.g., passive iron in nitric acid solution, local alteration 

 gives rise to a characterisitic spreading effect, which has a rate de- 

 pendent partly upon the composition of the medium, and partly upon 

 the pecuKarities of the tissue or metal. ^ The effects of local stimula- 

 tion in living tissues spreads to other parts at different rates, very rap- 

 idly in some tissues, e.g., nerve, while in others, e.g., smooth muscle, 

 the rate of transmission is slow. Similarly there is a wide varation 

 in the rate of electrolytic changes in metals under different condi- 

 tions.^- ^ The slow extension of a rust spot in iron in the presence 

 of an electrolyte is an instance of a gradual spreading effect; while 

 the change from the passive to the active state, in iron and other 

 metals, spreads from a region of local alteration, under certain con- 

 ditions, with great rapidity. i"- ^^ 



The general view that the bioelectric variation, as such, is the 

 essential change on which conduction of excitation in irritable 

 tissues depends is by no means a new one and was favored by du 

 Bois-Reymond, Hermann, Kiihne and other early students of the 

 bioelectric phenomena.^- 



The present investigation relates to the role of the composition 

 and electrical conductivity of the medium in the transmission of the 

 contraction-wave in muscle. 



^Lillie, R. S., Am. J. Physiol., 1916, xli, 126. 

 « Lillie,^ p. 129. 



^LilHe, R. S. Am. J. Physiol., 1914, xxxiv, 414; 1915, xxxvii, 348. 

 ^Lillie, R. S., Scient. Monthly, 1919, viii, 456, 552. Science, N. S., 1919, I, 

 259, 416. 



9 Lillie, R. S., and Johnston, E. N., Biol. Bull. 1919, xxxvi, 225. 

 ^^ Bennett, C. W. and Burnham, W. S., /. Phys. Chem. 1917, xxi, 107. 



11 Lillie, R. S., Am. J. Physiol., 1915, xxxvii, 348; 1916, xli, 126; /. Gen. Physiol., 

 1920, iii, 107. 



12 du Bois-Reymond, E., Ges. Ahhandl. dig. Muskel- mid Nervenphysik, 1888, 

 ii, 698, 733; Kuhne, W., Proc. Roy. Soc. London, 1888, xHv, 446; Z.Biol., 1888, 

 xxiv. 383. 



