28 PHYSIOLOGY OF MUSCLlv- AM" M-UVES. 



CHAPTER III. 



1. Jrrit.-il.ilil y of muscle; 2. Contraction and tetanus; ,'?. 



of elevation and performance of \\nrk; -I. Internal work during 

 tetanus; 5. Generation of heat and muscle-tone ; (',. Altrratimi 

 in form d.uriny o ml faction. 



1. If a muscle is cut from the body of a frog, and 

 i- fastened into the myograph just d< -scribed, it never 

 shortens spontaneously. If tin's docs seem to happen, it 



may safely be assumed that some accidental and uu- 

 pereeived external cause lias influenced it. A muscle 

 may, however, always be induced to shorten by 

 pinching it with tweexcrs, by smearing it with strong 

 acid, or by bringing certain other external influences, 

 the nature of which vie shall presently learn, to bear 

 upon it. Muscle, therefore, never shortens sponta- 

 neously, hut it can always be induce;! to do so. This 

 quality of muscle enables us to produce the state 

 of contract i. .11 at pleasure, and to examine accurately 

 (lie nature and method of tin; condition, \\hi,-h give 

 ri-e to it and the phenomena by which it i> accom- 

 panied. 



The myograph which, by means of the indicator 

 attached to it. marks the contraction of the muscle mi 

 the smoked glass plate, and at the. same time affords 



opport unity for measuring the extenl of the contraction, 



will presently prove of yet greater service. 1'ut for 



