MUSCLE FATIGUE. 217 



intervals. As the spring will give only a limited number 

 of contacts, let your co-worker manage it whilst you attend to 

 the muscle record. 



Keep the point off the drum until ready. Give the sign 

 for the spring to be set in operation, and at once bring 

 the point to bear upon the paper. Open S key and close 

 it again as soon as about 10 contractions have occurred. 

 When the curve has fallen, lift the point off the paper. 



The contractions will follow with regularity, and the curves 

 as they succeed each other will have the same height, but 

 will be cut short in their descent. The second contraction 

 of the series may be higher than the first, and the remainder 

 will be of the same height as the second. 



Take two more tracings, one with the clamp on the spring 

 half way, and the other with the same at the end of its 

 slide. Clamp firmly in position and re-adjust the needle each 

 time. 



The contractions occur more frequently at each shortening, 

 and the third curve, and possibly the fourth may rise higher 

 than before, the whole series being higher. Summation. 



3. Substitute the interrupter for the spring, the stimuli 

 will be more rapid and the curve will rise higher, be flat 

 topped and free of signs of separate contractions complete 

 fusion of them having occurred. 



It will not always be necessary to use the interrupter, 

 as it depends upon the condition of the frog, as to whether 

 so rapid a succession of stimuli will be necessary to produce 

 complete tetanus. 



Fatigue of Muscle. 10 



Required: Inductorium, muscle chamber and stand, two Leclanche 

 cells, 2 keys and 5 wires. Drum at a speed to draw the muscle 

 curve out to 2*5 cin , strong shocks. Nerveless muscle preparation. 



