The Acidity of Muscle during Maintained, Contraction. 407 



contact potential has been properly balanced. If there is no difference of 

 potential there cannot be any current, therefore there will be no polarisation. 



If acidity is related to tension in muscle it is necessary to show that 

 acidity remains when the muscle tension is maintained, and decreases when 

 the tension falls. In order to test the relation of acidity to muscle tension 

 two experimental procedures were tried. 



In the first, veratrin was painted on the frog's muscle after a record of the 

 normal contraction had been made. The out-standing feature of the action of 

 veratrin is that it does not affect the increase in tension of the muscle, but 

 that it delays the relaxation. 



With such a preparation the acidity, as shown by the manganese dioxide 

 electrode, remains also. Fig. 1 shows a muscle twitch of a fresh sartorius, 

 whilst fig. 2 shows the result with the same muscle after it had been treated 

 with veratrin (1 : 10 5 ). 



For the second procedure a decerebrate cat was used. This preparation 

 shows a marked tension (decerebrate rigidity) in the limb muscles. The 

 tension can be abolished by cutting the efferent nerves to the muscles, or by 

 reflex inhibition as the result of stimulation of an afferent nerve. 



In decerebrate preparations the rigid muscles show a greater acidity than 

 when the muscles are paralysed by cutting their efferent nerve supply, as 

 shown by the following results : — 



Table I. — Decerebrate Preparations showing Potential in Volts between a 

 Manganese Dioxide Electrode and a Calomel Electrode. 



Date. 



R. Sartorius. 



L. Sartorius. 



Rigid. 



After cutting 

 nerve. 



Difference. 



Rigid. 



After cutting 

 nerve. 



Difference. 



21.7.13 ... 



14.7.14 ... 

 8.3.21 ... 



-325 

 0-312 

 -355 



-004 

 -249 

 -206 



"321 

 -063 

 0-149 



0-186 

 0-249 

 0-866 



-0 -169 

 0-242 

 -771 



-355 

 -007 

 0-095 







Average "152 



Although the absolute values of these are unreliable it is clear that paralysing the muscle 

 always gives a result corresponding to a decrease in acidity. 



In order to demonstrate further that removal of maintained contraction 

 causes decrease in acidity, a reflex vasto-crureus preparation was used (3). 

 The sartorius was removed and the electrodes placed on the surface of the 

 vasto-crureus. On causing a reflex inhibition by stimulation of the ipsilateral 



