550 



PHYSIOLOGY. 



perhaps fats and proteids, and giving off carbonic acid. When the 

 muscle becomes active and does work, then the chemical changes 

 become more active. 



The chief differences between resting and acting muscle are: 

 (1) the acting muscle forms more C0 2 ; (2) more oxygen is consumed; 

 (3) sarcolactic acid is formed; (4) glycogen is made use of; (5) the 

 substances soluble in water diminish in amount,, while those soluble 

 in alcohol increase. 



CHANGES IN THE VOLUME OF THE MUSCLE DURING CONTRAC- 

 TION. Muscular contraction can be defined by its apparent effects: 



Fig. 195. An Experiment to Show that a Contracting Muscle does 

 not Change its Volume. (HEDON.) 



F, Vessel filled with water containing the frog's foot, the nerve upon two 

 electrodes, t, Capillary tube in which the level of the water is observed. P, 

 Battery. 



a shortening of the muscle. By experiment it has been shown that 

 the muscle on contracting simply shifts its muscular units when it 

 shortens, for the volume of the muscle remains the same. 



Muscle-wave. When a muscle is placed beneath two levers 

 some distance apart, and one end of the muscle is stimulated, then 

 a wave of muscular contraction runs through it. The distance 

 between the points at which the two curves begin to rise from the 

 abscissa gives the rate of wave-movement. 



The continuity of the muscle-fiber is the reason the wave is 

 propagated. The fibers stimulated are set into activity and the- 



