462 



GENERAL PHYSIOLOGY 



frequently in the cross-striated skeletal muscles of vertebrates. 

 Since by means of the graphic method muscular movement can be 

 recorded and its individual factors made visible, the progressive 

 fatigue of the muscle can be studied very conveniently in the 

 change undergone by the curve that the contracting muscle records. 

 Mosso ('91) has done this 'in the living man by means of his 

 ergograph, and has presented the results in his excellent and 

 fascinating book entitled " La Fatica" The ergograph is a small 

 apparatus in which the arm of a man is fastened by means of a 

 holder, while one finger is free to move. This finger is connected 

 by a cord with a writing-lever, which records upon a rotating drum 

 all the movements of the finger that take place, either voluntarily or 



FIG. 236. Mosso's-ergograph. (After Mosso.) 



involuntarily as the result of electrical stimulation. A weight 

 can be hung upon the cord, and thus the work performed by the 

 flexor muscles of the finger can be changed at will (Fig. 236). 

 By means of this apparatus it can be shown very clearly that, with 

 the stimulating induction-shocks remaining constant in intensity 

 and following each other at equal intervals, the work performed 

 by the muscles constantly decreases, and finally becomes equal to 

 zero. This is expressed in the curve of contraction, which gives 

 only the extent of the contraction, by a constant decrease in the 

 height of the lift (Fig. 237). After a course of contractions it 

 requires considerably stronger stimulation to produce further con- 

 traction of the fatigued muscles equal in height to that at the 

 beginning. The details of the changes are more readily visible 

 when the successive contraction-curves of a frog's leg are recorded 

 over one another upon a myograph from the beginning of the 



