748 THE PHYSIOLOGY OF THE CONTRACTILE TISSUES 



traction becomes less and less, but up to another limit the increase oi 

 weight more than compensates for the diminution of ' lift,' and the 

 work still increases. Beyond this, further increase of weight can no 



Fig. 254. Influence of Load on the Form of the Muscle Curve, i. curve taken with 

 unloaded lever; 2, 3, 4, weight successively increased; 5. abscissa line: time trace, 

 jfaf second (reduced). 



longer make up for the lessening of the lift, and the work falls off till 

 ultimately the muscle is unable to raise the weight at all. 



The ' absolute contractile force ' of an active muscle may be measured 

 by determining the weight which, brought to bear upon the muscle at 



Fig. 255. Influence of Temperature on the Striated Muscle Curve. 2, air tempera- 

 ture; i. 25 30 C. ; 3, 7 10 C. ; 4, ice in contact with muscle. The fifth curve 

 was taken at a little above air temperature. 



the instant of contraction, is just able to prevent shortening without 

 stretching the muscle. It, of course, depends, among other things, on 

 the cross-section of the muscle. During the contraction the absolute 

 force diminishes continually, so that a smaller and smaller weight is 



