(1ENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 115 



which has its normal blood-supply is rhythmically excited to a large Dumber 

 of contractions, but by the personal experience of every one accustomed to 

 violent muscular exercise. Everyone is conscious that he cannot put out the 

 greatest muscular effort until he has " warmed up to the work." The runner 

 precedes the race by a short run; the oarsman takes a short pull before going 

 to the line; in all the sports one sees the contestants making movements to 

 •'limber up" before they enter upon the work of the game. These prelim- 

 inary movements are performed not only to put the muscles in better c lition 



for action, but to ensure more accurate co-ordination — that is to say, the facts 

 ascertained for the muscle can be carried over to the central nervous system. 

 The finely adjusted activities of the nerve-cells which control the muscles reach 

 their perfection only after repeated action. 



In such experiments as that recorded in Figure 46 the record shows to 



Fir,. 47.— Effect of excitation upon the form of separate contractions. In this experiment the records 

 of the muscular contractions were taken upon a rapidly revolving drum. The muscle was the gas- 

 trocnemius of the frog; the contractions were Isotonic ; the weight was very light, about 10 grams; the 

 stimuli were maximal breaking induction shocks; and the rate of stimulation was twenty-three per 

 minute. 1 marks the first contraction; 2, the 100th; ;:, the 200th ; I, the 300th. The muscle was excited 

 automatically by an arrangement carried by the drum, and the excitation whs always given when a 

 definite part of the surface of the drum was opposite the point of the lever which recorded the con- 

 tractions. 



a remarkable degree the fact that at any given time the muscle has a definite 

 capacity for work. A suitable explanation of this is lacking. The corre- 

 spondence in the height of the contractions of the same group, and the differ- 

 ence in the height of different groups of contractions, must be attributed to the 

 existence within the muscle-cell of some automatic mechanism which regulates 

 the liberation of energy and which has its activity greatly influenced by the 

 alterations which result from action. Whether this supposed automatic regu- 

 latory mechanism controls both the preparation of the final material from 

 which the energy displayed by the muscle is liberated, and the amount of the 

 explosive change which results from the application of the irritant, cannot be 

 definitely said. 



(2) Effect of Frequent Excitations upon the Form of Separate Contractions. 

 — The effect of activity is not only observable in the change in the height 



