OP FUNCTION; OR, HOW WE ACT. 29 



as it reaches another, as shown in Fig. 6, until it 

 lias traversed the whole length exposed to view. 

 This is most probably the mode in which contraction 

 is effected during life; and in persistent muscular 



Fig. 5. 



Muscular fibre partly contracted, partly nncontracted. The increase in thickness, 

 and approximation of the striae, mark the state of contraction. 



Fig. 6. 



Striated muscular fibres contracting from irritation while under the microscope. 

 The contraction is seen travelling in wares in the direction of the length of the 

 muscle, and affecting chiefly its upper side. 



efforts it is believed that the different portions of 

 the muscle alternately relax and contract again, and 

 that all the fibres are not active together. The 

 contraction of muscle is attended with a slight 

 rustling sound, which may be heard by moving 

 the ball of the thumb vigorously, close to the ear. 

 In contracting, a muscle is not merely shortened; 

 it undergoes a change which modifies its entire 



