148 



Mr. H. E. Roaf. The Vapour-Pressure 



gives a concentration of 0*019 normal. To produce this concentration in the 

 25 c.c. of solution in the osmometer would require 5 c.c. of a decinormal 

 solution of lactic acid. It would be difficult to show the disappearance of 

 this amount from the 600 c.c. of- N/100 solution outside the osmometer. 

 In the last osmometer of the experiment 4 - 9 c.c. had disappeared, but such a 

 close result is probably a coincidence. 



If we wish to make a similar comparison in muscle we must calculate the 

 relative volume of the anisotropic substance to the whole muscle in the 

 uncontracted and contracted states. A disc of paper was divided into as 

 many smaller discs as possible by a cork borer. These smaller discs collec- 

 tively weighed - 581 grm., and the residue weighed 0"224 grm. It was 

 found, however, that there were certain larger pieces from the edge of the 

 large disc that were too small to form small discs. If these pieces were 

 excluded the weight of the residue was 0*153 grm. The larger the whole 

 disc the less relatively is the waste at the edges, so that we can consider 

 the weight of the smaller discs as between 79*2 and 72 - 2 per cent, of the 

 whole ; these weights represent the relative area of the combined smaller 

 discs to the whole disc. 



These figures give the relative volume of small cylinders inside a larger 

 cylinder of the same length. The volume of an ellipsoid is two-thirds of a 

 cylinder of the same length and diameter. Therefore the volume of the 

 ellipsoids will be two-thirds of the above, namely, between 52*8 and 48 - l per 

 cent, of the volume of the dim band. As the volume of the light band is 

 approximately the same as that of the dim band, the ellipsoids will occupy 

 half the above amount, that is between 26'4 and 24 - l per cent, of the uncon- 

 tracted muscle. 



In the contracted condition the whole of the muscle is contained in the 

 dim band, and the ellipsoids become spheres. In the preceding paragraph 

 we have calculated the relative volume of cylinders inside a larger cylinder, 

 and since the volume of a sphere is two-thirds of the volume of a cylinder 

 surrounding it, we see that the spheres occupy between 52 - 8 and 48*1 per 

 cent, of the whole contracted muscle. 



If as in the osmometer experiment the concentration of lactic acid in the 

 isotropous substance remains as low as - 01 normal, and the concentration in 

 the whole muscle is equivalent to 0-025 normal (5), we can calculate the 

 amount of lactic acid in the anisotropous substance. If the muscle is 

 prevented from shortening, the concentration would be about - 07 normal. 

 If, on the other hand, the muscle is allowed to shorten, the concentration of 

 lactic acid in the anisotropous substance would be about - 04 normal. These 

 figures are obtained by subtracting from the total concentration of lactic acid 



