PRODUCTION OF TETANUS. 181 



B. (a.) Arrange an induction coil and commutator as 

 before. 



(b.) Prepare a nerve-muscle preparation, with a straw-flag 

 as before, and place its nerve over the du Bois electrodes 

 attached to the commutator. Pass two fine wires through 

 the gastrocnemius, and attach them to the other two binding 

 screws of the commutator. 



(c.) Tetanise the nerve until the tetanus ceases. Then 

 reverse the commutator and stimulate the muscle. It con- 

 tracts. Therefore, in this case, the seat of fatigue is not in 

 the muscle. 



LESSON XXXVI. 



PRODUCTION OF TETANUS METRONOME 

 THICKENING OF A MUSCLE. 



1. Production of Tetanus. The tetanising current may be made 

 and broken with the hand, by Neef 's hammer, or by means of a 

 vibrating rod. Apparatus. Daniell's cell, five wires, flat spring, 

 cup of mercury in a wooden stand, induction machine, du Bois 

 key, moist chamber and muscle lever, recording drum moving 

 at a medium speed. 



(a.) Arrange the experiment as in Fig. 73 ; the induction 

 machine for single shocks, short-circuiting the secondary 

 circuit. Place in the primary circuit the flat metallic spring, 

 held in a wooden clamp. One end of the spring has a needle 

 fixed at right angles to it, which dips into a cup of mercury 

 fixed in a wooden stand. The needle hangs just above the 

 mercury cup when the spring is at rest, but dips in and out 

 of the mercury when it vibrates. The clamped end of the 

 spring is connected with the battery, while the mercury cup 

 is connected with the induction machine. Cover the mer- 

 cury with alcohol and water (1:3) to prevent oxidation, 

 and to keep the resistance more uniform. 



