HABIT FORMATION IN THE ALBINO RAT 9 



surface. The central shade is circular, those for the peripheral 

 lights are half shades. 



The floor of the maze is covered with white linoleum, which 

 can be thoroughly scrubbed whenever necessary. The entrance 

 to the starting box is supplied with a hinged door which can be 

 securely fastened after the animal has been placed inside. The 

 exit is provided with a sliding door which is raised by means 

 of a cord, and closes of its own weight when the tension on the 

 cord is released, thus making it impossible for a rat to return 

 into the starting box after it has once entered the maze. 18 



By means of the two mirrors (M and M'), and the lens (L), 

 an exact image (I M) of the maze is thrown on the recording 

 table where the experimenter can follow every movement of the 

 animal during any passage through the maze. Actual records 

 of these trips are made by tracing on the record sheet with a 

 soft pencil the successive movements of the rat. (See Fig. 2). 

 These tracings, measured with a chartometer shown by 

 calibration to be accurate to within one per cent, form the 

 basis for the distance record. Since the maze is six and four 

 tenths times as large as the image, the distance record obtained 

 in centimeters by the chartometer, must be multiplied by six 

 and four tenths to obtain the actual distance traversed in the 

 maze. For example, if the distance indicated by the char- 

 tometer is one hundred and twenty-one centimeters we 

 obtain the actual distance run, thus, 121 centimeters x 6.4 = 

 774.4 centimeters. The values given in the tables represent the 

 actual distance covered by the rats. Both chart and maze 

 distances were tabulated, and the multiplications made to ob- 

 tain the latter were checked on the adding machine. In addi- 

 tion to the distance record, such charted pathways also furnish 



18 The maze was used exactly as described above throughout the work in order 

 to maintain the same experimental conditions for all the groups. However, in 

 the course of the experiments, several possible improvements suggested them- 

 selves as being desirable: 



First. The maze should be constructed of such material that it could be frequently 

 flushed out with a hose, and a plug should be fitted into the bottom to facilitate 

 cleaning. 



Second. Nitrogen lamps placed at crossfire above the maze would be better 

 than the tungstens surrounding it, and would do away with the shadows caused 

 by the aluminum shades, which, when a very small animal is the subject in the 

 maze, are troublesome. 



Third. A change in the lighting arrangement would make it possible to have 

 the mesh top made in two pieces instead of four, and hinged to the sides of the 

 maze so that it could be lifted easily and noiselessly, thus avoiding frightening 

 the animal within the maze. 



