278 ADVANCED PHYSIOLOGY 



that each muscle must be contracted to just the right 

 amount at just the right moment, or the ball will go 

 wide of the mark. To insure the harmonious action of all 

 these muscles so that the ball will go exactly where it is in- 

 tended, requires a most wonderful control. One does not, 

 of course, have any consciousness that he is regulating all 

 these muscles. He simply decides to throw the ball, but the 

 brain unconsciously so regulates the stimuli sent to the 

 muscles that they act in the order to produce the desired 

 result. "Practice makes perfect," simply because the brain 

 has had the opportunity of learning to exercise this wonder- 

 ful control over the actions of the numerous muscles. 



Tetanus of Striped Muscles. The term tetanus, although 

 not so familiar, has much the same meaning as the word 

 "cramps." When one keeps a muscle contracted as, for 

 instance, when he holds a weight at arm's length, he does 

 this by sending stimuli into the muscles very rapidly, ten to 

 twenty per second so rapidly that the muscle does not have 

 time to relax between the successive stimuli. As long as 

 these stimuli continue, the muscle remains contracted, i.e. in 

 a condition of tetanus. All of our muscle actions are really 

 of this character. Sometimes, when a muscle is tired and 

 perhaps quickly cooled by plunging into cold water, it is 

 thrown into a similar state of contraction or tetanus without 

 one's willing it or being able to stop the contraction. We 

 then call it " cramps," but it does not differ from ordinary 

 tetanus, except that it is not voluntary. 



Effects of Heat and Cold on Muscle Action. A jockey 

 drives his horse a couple of miles or so before putting him into 

 the race " to get him warmed up," and athletes for the same 

 reason take some gentle exercise before undertaking the 

 actual contest. 



Whether the benefit of these preliminary exercises 

 really due to the warming of the muscles or to an increased 



