THE CHANGE IN FORM 357 



Simple Contraction. Prepare a second ring 

 of frog's stomach in the manner described in 

 the preceding experiment. Attach the lower 

 margin of the ring to the muscle lever by means 

 of a fine copper wire. Carry the end of the 

 copper wire to the binding post on the muscle 

 lever. Connect this post and the post on the 

 muscle clamp with a dry cell, interposing a sim- 

 ple key. Place the electro-magnetic signal in the 

 primary circuit. Bring the writing points of the 

 muscle lever and the signal against a smoked 

 drum in the same verticle line. Let the drum 

 move at slow speed. Stimulate the muscle by 

 making and breaking the galvanic current once, 

 not oftener. 



Compare the duration of the latent period with 

 that of skeletal muscle. Compare the form., of 

 the contraction curve with that of skeletal 

 muscle. 



Tetanus. Determine how frequent the stimuli 

 must be in order that the separate contractions 

 may be fused into a smooth curve. 



Usually the muscle after contracting loses its 

 irritability for several minutes. If this occur, 

 the ring may be laid aside, covered with filter 

 paper saturated with normal saline solution. 

 Excellent curves are often obtained from muscle 

 preserved in this way for half an hour or more. 



