BEHAVIOR OF STOCK AND INBRED ALBINO RATS 271 



lowed with a pencil on successive sheets. In early tests of a 

 rat frequently seven or eight sheets would be used for one 

 record. The record thus obtained was traced with a Keuffel 

 and Esser chartometer, and the result was a record of the dis- 

 tance, in centimeters, of the path as projected on the paper. 

 The ratio of the size of the image to that of the maze was as 

 1 to 6.75. The number of centimeters as recorded by the charto- 

 meter was therefore multiplied by 6.75 to obtain the actual 

 distance covered by the rat. The distance is given in centi- 

 meters in the accompanying tables. 



In preliminary experiments, in order to remove possible error 

 due to fear of the strange environment, all blocks shutting off 

 the blind alleys were removed and the animals allowed to roam 

 at will throughout the maze, finding their way to the food in 

 the center if possible. One such trial a day was given for three, 

 or five, days prior to the regular experiments. Later, the better 

 expedient was adopted of feeding the animals in the food box 

 in the centre of the maze for twenty minutes each day for three 

 to five days. When the regular experiments were begun with 

 the long form of maze the rats were allowed to feed in the centre 

 for five minutes after completing the circuit and were then 

 given additional food in the cage. In the short form of maze 

 the animals were fed only in the food-box for twenty minutes 

 at the close of the day's work. By the latter method it was 

 possible to regulate better the amount of hunger which served 

 as an incitement to activity in traversing the maze, but it is 

 possible that with only one such trial a day the animals were 

 underfed. This may account for their small size, as noted later. 



The habit was considered perfect when a rat made three cor- 

 rect runs in succession, i.e., runs in which there were no errors. 

 The distance for the shortest path in the long maze was 556.88 

 centimeters; in the short maze, 357.75 centimeters. 



In the preliminary experiments a rat was allowed thirty 

 minutes in which to find the way into the centre. Later this 

 was reduced to fifteen minutes, since it was discovered that 

 almost invariably, if the rat had not succeeded within the first 

 fifteen minutes, it spent the remainder of the time sitting still 

 in a corner or doorway. The figures followed by a -f- in the 

 time columns of the tables indicate that a rat was given the 

 full allowance of time and then removed for the day. When 



