INFLUENCE OF LOAD. 219 



By successive addition of separate weights. Adjust the 

 muscle to record a maximal contraction. Take records of 

 successive contractions, moving the drum by hand between 

 each for 5 Ium . After the movement from each contraction 

 has subsided, turn the drum to a fresh place, half a cm 

 from the preceding, add a 10 gramme weight, and as soon 

 as the extension caused by this is complete move the drum 

 another half cm, stimulate and note that the writing point on 

 extension of the muscle falls below the point from which 

 it started. Proceed in this manner until the muscle curves 

 are extinguished. Compare the relative heights of the various 

 contractions, and make an approximate calculation of the 

 work done by the muscle, in gramme millimetres, by measuring 

 the height of each contraction in millimetres, and multiplying 

 in each case by the number of grammes lifted. The work 

 will rise with increase of the weight up to a certain point, 

 and will then fall. 



Isometric method. Contraction performed under a rapidly 

 and equably increasing load. 



Required: Drum, muscle chamber on stand, strong spring fixed to 

 a bar held in a clamp upon the side bar as in Fig. 40, 1. Direct 

 stimulation of the muscle by drum contact. Speed of drum to draw 

 the muscle curve out to 4'5 cm . Inductorium, 2 Leclanche cells, 2 keys, 

 7 wires, and 2 fine. 



In adjusting the muscle let it be under slight tension, so 

 that there should be no slack to take up at the first moment 

 of its contraction. 



After the first contraction has been recorded, increase the 

 tension by lowering the side bar 2 or 3 mm . Readjust the 

 writing point to the original abscissa. Repeat the process 

 after each contraction. 



It will be found that, within narrow limits, the contraction 

 will be increased by the magnification of the load, and by 



