4 G. V. HAMILTON 



out as clean-cut entities : response often consists of manifold 

 activities which lack a common objective reference. The task 

 of identifying relatively separate types of reaction is, therefore, 

 a difficult one, and is not apt to appeal to the investigator who 

 is impatient to have done with roughly exploratory methods 

 and to apply only highly exact ones. At this point it is to 

 be remembered that in a technological field of comparative 

 psychology — psychoanalytic psychopathology — a rough and ad- 

 mittedly often unnecessarily crude exploration is currently 

 revealing material for behavioristic investigation, the existence 

 of which was barely if at all suspected by certain psychopatholo- 

 gists who were and still are committed to the exclusive use of 

 highly exact methods. I can think of no better justification of 

 a method that is exploratory in intention and that seeks to 

 prepare a way for the identification of reactive tendencies than 

 is contained in Holt's (2) statement that Freud has given us 

 " the first key which psychology has ever had which fitted, 

 and moreover I believe that it is the only one that psychology 

 will ever need." 



Apparatus for Rodents. — Figure 1 gives a view of the appa- 

 ratus as a whole. Its essential feature is a semicircular enclo- 

 sure, which is built on a table top. The walls of this enclosure 

 are interrupted by five apertures. The one that divides the 

 straight part of the wall into two equal parts is shown as 

 blocked by a box in fig. 1, and can best be seen in fig. 2. This 

 aperture is for entrance. The curved part of the wall is broken 

 by four apertures, each of which opens into its own exit way 

 or alley. 



Figure 2 gives the plan of the entire table top, and is there- 

 fore a floor plan of the semicircular enclosure, the entrance and 

 exit alleys, the bases of the wall and the parts of the table top 

 that lie outside the wall. The shaded parts of the figure marked 

 with W's represent the bases of the enclosure walls, which are 

 also the walls of the alleys. The bases or bottoms of these box- 

 like walls are of 1-inch redwood, as are also their tops, which 

 are of the same dimensions. They afford attachment for vertical 

 sides of sheet tin. The horizontal dimensions of the walls are 

 given in fig. 2. The sides have a uniform elevation of 15 cm. 

 The curved wall forms a half circle, and has a 36 cm. radius. 

 Reference to fig. 2 will show that the exit alleys are equidistant 



