I02 Physico-Chemical Basis of Striatcd Musclc Contraction [Sept 



n/20) it contracts. On replacing the acid Solution by water, the 

 string relaxes. The relaxation is faster, however, when the acid 

 is replaced, not by water, but by a Solution of some salt such as 

 sodium bicarbonate, which can neutralize the acid. From their 

 diagrams it would seem that a minute or more may be required for 

 a Single contraction or relaxation, depending upon the strength of 

 the acid, etc., etc. 



These observations are, no doubt, interesting in themselves. 

 But before connecting them with muscle contraction, might it not 

 be well to consider whether the conditions under which a catgut 

 string can contract and relax are at all similar to those existing in 

 muscle ? 



Strietman and Fischer State that because lactic acid is formed 

 in a working muscle and because a catgut string will contract when 

 immersed in a lactic acid Solution and will relax when the acid is 

 removed, therefore, in the working muscle, the contraction is 

 brought about by the formation of lactic acid. They quote several 

 other investigators who have stated their belief in the same idea of 

 the connection between lactic acid formation and contractility with- 

 out, however, making any of the simple calculations that would 

 naturally suggest themselves. 



Their theory is open to the following objections: (i) It is not 

 likely that there is any free lactic acid in the working muscle, it is 

 probably neutralized at once by the phosphates present in lymph. 

 At least this would be inferred from the work of Henderson^ who 

 showed that the mixture of phosphates and other substances in blood 

 and various tissue fluids was such as to enable them to maintain 

 an absolute neutrality in spite of the formation of even considerable 

 quantities of acid or of alkali. This point was not overlooked by 

 Zuntz (p. 20, 1. c.) when calculating the amount of energy made 

 available by the transformation of dextrose into lactic acid. The 

 heat of neutralization of the lactic acid by sodium, as well as the 

 heat required to separate the sodium from its presumable combina- 

 tion with protein, are given due consideration by Zuntz, who cal- 

 culated that the heat liberated in the formation of lactic acid from 

 dextrose is equivalent to 3.4 per cent. of the heat of combustion of 

 dextrose. 



* Henderson, L. J. : Ergebnisse d. Physiologie, 1909, 8, 254-325. 



