THE PHYSICO-CHEMICAL BASIS OF STRIATED 

 MUSCLE CONTRACTION 



3. The maximum surface tension in striated muscle 



WILLIAM N. BERG 



Introduction 



About a year ago, the writer^ publisht some calculations on the 

 lifting power of striated muscle, in which an attempt was made to 

 ascertain whether the changes in the surface tension between the 

 contractu units and their surrounding medium were great enough to 

 account for the hfting power of striated muscle. 



Among others, the assumption was then made that at the mo- 

 ment when a striated muscle begins to contract against an external 

 resistance, the surface tension between the contractu units and their 

 surrounding medium (presumably the sarkoplasm) might possibly 

 be as high as 85 dynes per cm. This was regarded as the upper 

 limit, altho certain data in the literature, to be presented later, 

 plainly indicated that the Upper limit could not be so high. Several 

 assumptions were made in favor of the surface-tension theory for 

 the purpose of justifying the temporary or provisional use of 85 

 dynes per cm. as the maximum surface tension between the con- 

 tractu units and sarkoplasm. A minimal surface tension was like- 

 wise assumed from the literature for the relaxation phase, but as 

 this figure was purposely and provisionally omitted from the final 

 calculations, it may be disregarded for the present. 



The results indicated that in a working striated muscle, surface 

 energy can furnish but a small part of the total energy transformed, 

 a conclusion diametrically opposed to that of Bernstein, Macallum^ 

 and others, who regard a working muscle as a mechanism that can 

 transform a quantity of surface energy equivalent to the external 

 work done. 



1 Berg: Biochemical Bulletin, 1912, ii, p. loi. 



2 Macallum : Jour. Biol. Chem., 1913, xiv, p. 96. 



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