224 



PRACTICAL PHYSIOLOGY. 



[XLI. 



(6.) Note the '* staircase" character of the curve, i.e., the second con traction 

 is higher than the first, the third than the second, and so on tor a certain 

 number of contractions. After that the height of the contraction falls 



Fig. 147.— Tetanns-Curve produced with break shocks stimulation every second by means 

 of an automatic break key in the primary circuit. T. Time-curve, 100 D.V. per 

 second. 



steadily, so that a line uniting the apices of all the contractions forms a 

 straight line approximately. 



In a fatigue-curve, where only the "lift" is recorded, note that the rise of 

 the lever increases with the number of stimuli — the strength of the stimulus 

 remaining constant, so that one gets the phenomenon of the "Treppe" or 

 "staircase." After a time it falls steadily until the excitability is ex- 

 tinguished (fig. 148). Note also that in the phase of relaxation the lever does 

 not reach the abscissa, i.e., relaxation takes place so slowly as if one had to 



FlQ. 148. — Fatigue-Curve of an Excised Frog's Muscle recorded on a Slow-moving Drum. 



deal with a so-called "contracture," li the march of events be arrested, and 

 time given for rej)ose, then, on stimnlating, tne lift increases, but the effect 

 lasts only for a short time. 



