PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 501 



ent points to the view that potassium and phosphorus easily 

 escape from the Uving muscle fibers, and that this loss is repaired 

 by the entrance of these two substances into the fibers in some 

 combination or combinations other than potassium phosphate.^ 

 It is not doubted by biological chemists at present that the striated 

 muscle fibers contain considerable quantities of phosphorus in 

 organic combination. 



The question how the muscle fibers are kept free or nearly free 

 of sodium and chlorine cannot profitably be discussed at present, 

 as there is no existing experimental evidence on the subject. It 

 seems probable, however, that chemical as well as physical fac- 

 tors play a part in the maintenance of this condition also. 



Overton has explained some of the facts observed by him by 

 supposing that a certain portion of the water within the muscle 

 fibers is held in chemical combination by the colloids as organic 

 water, and does not act as a solvent for the muscle salts.** He 

 does not, however, give a detailed consideration to this part of 

 the subject, leaving untouched the question whether the amount 

 of the organic water is variable or constant. A good many facts 

 could be explained by supposing the quantity of the organic 

 water to be variable. 



Schwarz has recently reported a number of experiments which 

 indicate that any influence that causes a muscle to produce lactic 

 acid tends to make it take up fluid from an isotonic salt solution. ^ 

 It seems improbable that the muscle's increased tendency to 

 take up water is the direct result of the increase in the osmotic 

 pressure of the muscle contents brought about by the presence 

 of the lactic acid. In the first place, the osmotic pressure of such 

 quantities of lactic acid as could be produced under the condi- 

 tions of Schwarz 's experiments would be infinitesimally small in 

 comparison to the osmotic pressure of the muscle salts; and in 

 the second place, Overton has found that the muscle membranes 

 are quite permeable to lactic acid.^« An alternative explanation 

 would be that the acid acts to make the muscle colloids combine 



^ See Meigs and Ryan, Jour. Biol. Chemistry, 1912, vol. 11, pp. 409 and 410. 

 8 Overton; Archiv flir gesammte Physiologie, 1902, Bd. 92, pp. 128-142. 

 ^ Schwarz; Biochemische Zeitschrift, 1911, Bd. 37, p. 34. 

 10 Overton; Archiv fur die gesammte Physiologie, 1902, Bd. 92, p. 267. 



