GENERAL PHYSIOLOGY. 71 



duced circuit caused by a closure of the battery- 

 circuit will stimulate the preparation. 



(/) Close the short-circuiting key in the secondary 

 circuit. 



(d) Open or break the primary circuit. An induced 

 break shock occurs in the secondary circuit but it 

 is short-circuited by the closed Du Bois Reymond 

 key. If while the drum rotates one makes, in 

 close succession, the changes above indicated 

 a-b-c-d-a-b-c-d etc. there will be produced a 

 series of contractions, all the result of stimulation 

 by make induction shocks. 



(2) Take a tracing of the contractions resulting from 

 a series of indirectly applied break induction shocks. 



(3) By leaving the short-circuiting key open, one may 

 get a series of contractions due to alternating make 

 and break induction shocks. Let these be re- 

 corded in pairs upon the kymograph. 



(4) Determine the distance which the secondary coil 

 may be removed from the primary coil and get any 

 response to the make or break. Which is more 

 effective make or break ? Can one find a position 

 of the secondary coil where there are only make or 

 break shocks? What are the limits of this position ? 

 Within the limits of that position where both make 

 and break contractions occur are there differences 

 in the height of the make or break waves? Is there 

 a position of maximum height for both waves ? If 

 not, is there a position of maximum height for each 

 wave ? 



Make a tracing on a slowly rotating drum, while 

 gradually moving the secondary coil from the great- 

 est distance which gives a contraction up to the 

 zero point. Record at intervals upon the tracing 



