D. B. CASTEEL 



screen allows the operator to observe fully the actions of the 

 animal without himself being seen or in any way influencing 

 the animal's behavior. Upon each insulated electrode, well 



Fig. 1 — General view of apparatus. 



toward the back, is fastened a piece of cork behind v/hich meat 

 may be placed. The cork is of such shape that it acts as a blind, 



