CHANGES IN ELECTRICAL STATE. 457 



the quantity of CO 2 has no exact relation to that of the oxygen 

 used. 



5. A diminution is said to occur in the contained glycogen, 

 and certainly prolonged inactivity causes an increase in the 

 amount of glycogen. 



6. A peculiar muscle sugar makes its appearance. 



Change in Elasticity. The elasticity of a muscle during its 

 state of contraction is less than when it is in the passive state. 

 That is to say, that a given weight will extend the same muscle 

 more if attached to it while contracted (as in tetanus) than when 

 it is relaxed. The contracted muscle is then more extensible. If, 

 then, a weight which is just over the maximum load the muscle 

 can lift, be hung from it and the muscle then stimulated, it should 

 become extended, because the change to the active state lessens its 

 elastic power, while it cannot contract, being over-weighted. 



Electrical Changes. If a muscle, in connection with a galvan- 

 ometer, so as to show the natural current, be stimulated by means 

 of the nerves, a marked change occurs in the current. The gal- 

 vanometric needle swings toward zero, showing that the current 

 is weakened or destroyed. This is called the negative variation 

 of the muscle current which initiates the change to the active 

 condition. When the muscle receives but a momentary stimulus 

 so as only to give a single contraction, this negative variation 

 takes place in the current, but, owing to its extremely short dura- 

 tion, the galvanometric needle is prevented by its inertia from 

 following the change. Only the most sensitive and well-regulated 

 instruments show the electric change of a single contraction, but 

 when the muscle is kept contracted by a series of rapidly repeated 

 stimulations then the inertia of the needle is- readily overcome. 

 The negative variation of a single contraction can, however, be 

 easily shown on the sensitive animal tissues. For this purpose 

 the nerve of one nerve-muscle preparation* is placed upon the 

 surface of another muscle so as to pass over the middle of the 



* By a nerve-muscle preparation is meant a muscle of a frog (com- 

 monly the gastrocnemius and the half of the femur to which it is attached ) 

 and its nerve which has been carefully separated from other parts and 

 removed from the body. 

 39 



