101 



Note the "staircase" character of the record, i. e., the 

 second contraction is hig-her than the first, the third than the 

 second and so on for a certain number of contractions. After 

 that the heig^ht of the contraction falls steadily so that a line 

 uniting the apices of all of the contractions forms a straight 

 line approximately. Note later that in the phase of relaxation 

 the lever does not reach the abscissa. If the march of events 

 be arrested, and time given for repose, then, on stimulating, 

 the lift increases, but the effect lasts only for a short time. 



After the gastrocnemius muscle is thoroughly fatigued 

 cut across the middle of the muscle with, a scalpel and test 

 with litmus paper the area of the cross section thus exposed. 

 Test in the same way a cross section of the sartorius or some 

 other muscle which has not been fatigued. 



346. Tetanus. Prepare a nerve-muscle preparation. 

 Arrange to record on drum with the smallest fan. 



Place a key in the primary circuit, also one in the secon- 

 dary and wire for interrupted current. Adjust the special 

 wire and weight in the vibrating hammer, so that it swings 

 at its lowest and gentlest rate. Open the short-circuiting key 

 in the secondary circuit. Make the current for very short 

 intervals in the primary. Adjust the weight so as to get faster 

 vibrations and compare. 



Fig. 25. 



Fig. 25. Curve of tetanus. At the beginning ad, the individual contrac- 

 tions are somewhat discernible ; these disappear and the general level of the 

 curve rises to e. At this point the stimulus was removed and the curve dropped 

 quickly toward the base line. 



Study the tracings. The first are indented but gradually 

 there is more and more fusion of the teeth until a curve un- 

 broken by depressions is obtained. In the curve of complete 

 tetanus the ascent is at first steep then slightly more gradual, 

 speedily reaching a maximum, when the lever practically 



