344 THE OUTGO OF ENERGY 



water. Direct electrical stimulation of the muscle 

 may be made by connecting one electrode with the 

 metal parts of the apparatus and the other with the 

 copper wire attached to the upper end of the muscle. 



Note that as the temperature falls the contrac- 

 tion curve becomes longer. The phase of rising 

 energy is lengthened more than the relaxation. 

 The earlier portion of the relaxation is lengthened 

 less than the later ; the muscle shows a tendency 

 to contracture (see page 340). 



Place fresh paper on the drum. Let the drum re- 

 volve very slowly. Place a lighted Bunsen burner 

 under the arm of the muscle warmer. At intervals 

 of 5 stimulate the muscle with a maximal break 

 current. Note the changes in the contraction. 



The height of contraction is least at the freezing 

 point of the muscle (-5). It rises from the 

 freezing point to 0; falls from to 19; in- 

 creases to 30, which is the maximum ; from 30 

 to 45 diminishes again; and at 45 the frog's 

 muscle usually enters into a state called rigor 

 caloris; the muscle becomes opaque, inelastic, 

 resistant to the touch, shortens very considerably, 

 and undergoes chemical changes of great impor- 

 tance. The duration of contraction lessens with 

 the rising temperature, being least at 30. Above 

 30 the duration remains approximately un- 

 changed. The latent period is increased at low 



