io6 Physico-Chemical Basis of Striatcd Muscle Contraction [Sept. 



a biiilding do no work in the physical sense, n'or would a man 

 who took the place of one of them; altho physiologically he would 

 do a great deal of work. In this case the distance thru which the 

 force acts (the weight supported or the upward thrust of the man's 

 Shoulders) is zero and hence the work is zero. The above equa- 

 tions of Bernstein could be made consistent if there were two 

 factors on the left-hand side; one, the surface tension or change in 

 surface tension (expressed in dynes per cm.), the other, the area or 

 change in area (expressed in cm.^). The product (ergs) could be 

 calculated to calories (gram-degrees C.) by dividing by 4.2 X 10''^, 

 since i small calorie (gram-degree C.) is equivalent to 4.2 X 10'^ 

 ergs. It is difficult to see what the other factor (omitted by Bern- 

 stein) can be. In an isometric tetanus the muscle does not change 

 its length. In what way can an internal diminution in area take 

 place? If the contractu units — whatever their shape may be — do 

 not change in length, how do their areas diminish? This difficulty 

 does not arise in the case of the ordinary (isotonic) contraction. 

 Here one can assume a decrease in the areas of contact between 

 contractil unit and sarkoplasm caused by an increase in the surface 

 tension between the same surfaces. The product of these two 

 quantities, according to the theory, should be an amount of work 

 sufficient to account for the external work done and perhaps also 

 for the heat liberated at the same time. 



We have stated before that Bernstein's calculations on the 

 magnitude of the surface energy changes in muscle are probably 

 unnecessarily complex, involving, as they do, several pages of cal- 

 culus. The same result is obtained in the following calculations, in 

 which two simple quantities are calculated and then compared : 

 (i) the amount of energy liberated in a working muscle thru in- 

 crease of surface tension times diminution of area of contractil 

 Units; and (2) the external work done in lifting a weight a known 

 distance. 



Assume that in i c.c. of muscle a right section contains (as 

 Zuntz assumes, 1. c, p. 24) 62 million rods, and that there are 800 

 such layers, making a total of very nearly 5 X 10^^ rods in i c.c. of 

 muscle. Assume the general structure of muscle to be that de- 

 scribed by Hürthle (see diagram), and that the muscle rod is the 



