PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 549 



the shortening of the smooth muscle fibers is the direct mechanical 

 result of this decrease in volume. 



The question how the relaxation of smooth muscle is brought 

 about is bound up with the question how the presence of acid 

 could decrease the tendency of the smooth muscle colloids to 

 take up or hold water; and on this question there is as yet practi- 

 cally no experimental evidence. But the supposition that the acid 

 acts to neutrahze an already present sUght alkahnity of the col- 

 loids suggests an interesting explanation of certain of the physio- 

 logical pecuHarities of smooth muscle. It may be supposed that 

 the combination of the acid with the alkahne colloid is compara- 

 tively stable, and that the resulting state of decreased alkahnity 

 can be made to disappear only by some further slow chemical 

 process by which the lactic acid, radicle is either further oxidized 

 or otherwise got rid of. This supposition would furnish a pre- 

 liminary rough explanation of the slowness with which relaxation 

 often occurs in smooth muscle, and of the tissue's power of remain- 

 ing for an indefinite period in a state of high tonic contraction. 



PROTOCOLS OF THE EXPERIMENTS 



Experiment 1 



November 3, 1909 

 Sartorius from frog 1, weighed fresh 0.082 gram 

 11.53 A.M. immersed in distilled water 3.53 p.m. weighed 0.127 gram 

 12.23 P.M. weighed 0.135 gram 6.10 p.m. weighed 0.129 gram 



12.53 P.M. weighed 0.124 gram 7.59 p.m. weighed 0.128 gram 



1.53 P.M. weighed 0.120 gram 9.14 p.m. weighed 0.125 gram 



2.53 P.M. weighed 0.126 gram 10.38 a.m. Nov. 4, weighed 0.124 gram 



Temperature varied between 19° and 20° 



Experiment 2 



November 29, 1909 



Sartorius from frog 2, weighed fresh 0.154 gram 

 10.55 a.m. immersed in distilled water 11.20 a.m. weighed 0.246 gram 

 11.00 a.m. weighed 0.218 gram 11.25 a.m. weighed 0.238 gram 



11.05 a.m. weighed 0.238 gram 11.40 a.m. weighed 0.226 gram 



11.10 a.m. weighed 0.248 gram 11.55 a.m. weighed 0.215 gram 



11.15 a.m. weighed 0.251 gram 



Temperature varied between 19° and 20° 



