70 



EXPERIMENTAL GENERAL PHYSIOLOGY 



the figure. Note that the nerve from muscle // touches muscle / in 

 two places at the end and middle. Set up the electric apparatus 

 for single-induction shocks and rest the nerve of muscle I upon the 

 electrodes. 



FIG. 42 



"The rheoscopic frog," an experiment to show the presence of the difference of electric 

 potential in different parts of an active muscle. 1. The active muscle, stimulated at E by 

 induction shocks. II. The second preparation, which can be thrown into contraction only 

 through some influence exerted at the points of contact (Xand Y). Note that the muscles lie 

 upon glass plates (Gand G"), and that a glass nerve hook rests upon Jin order to ensure two 

 separate points of contact of the nerve from II. 



3. Observations. (1) Rule a table as follows: 



Response. 



(2) Stimulate muscle I as indicated in the table and record the 

 response in the proper column. 



(3) What portion of preparation I is traversed by the electric 

 current ? 



(4) Does any portion of the stimulating current traverse that part 

 of muscle / between the points X and Y. 



(5) What causes the contractions of muscle II f Preparation // 

 is called a rheoscopic preparation or a physiological rheoscope. If 

 the contractions are caused by electricity one should be able to 

 detect it through the use of the galvanometer or electrometer. 



