THE HARVARD LABORATORY OF ANIMAL PSYCHOLOGY 179 



Yerkes and Kellogg graphic record device. The latter enables 

 an observer to obtain accurate records of distance and errors, in 

 addition to those of time, in all maze experiments. Thus, the 

 value of the maze-method is 1 trebled. This improved apparatus 

 demands stability, and, although it may readily enough be moved 

 from room to room, it is eminently desirable to have a suitable 

 place reserved for it, so long as the maze method maintains its 

 present importance and promise as a comparative method and 

 offers so many obvious possibilities of improvement. 



The rooms numbered 43, 44 and 45 are daylight rooms as is 

 also 42, which may be employed as occasion demands. At 

 present, two of them are used for studies of problems of heredity 

 in rats and mice. Later, the Hamilton insoluble problem multi- 

 ple choice apparatus and the Yerkes soluble problem multiple 

 choice apparatus will be installed in this group of rooms. These 

 devices demand a special recorder-room. It is our purpose to 

 install the recorder for both outfits in one room while placing 

 the respective reaction devices in separate rooms. These two 

 sets of multiple choice apparatus will render possible in this 

 laboratory or at the Field Station (since we propose so to construct 

 the apparatus that it shall be readily movable) the study of 

 ideational reactions, in a variety of animal types, in such wise 

 as to furnish directly comparable data of reaction. 



The line of dark-rooms numbered 46, 48 and 49, is especially 

 convenient because it may be used either in sections or as a whole. 

 A supply of compressed air is delivered to room 49, and it is in- 

 tended that in this room, in conjunction with room 48, there shall 

 be installed apparatus demanding air under constant pressure 

 for varied studies of olfaction and audition. 



A store room, number 47, provides adequate space for supplies 

 in the shape of food stuffs, bedding or litter, small cages, and 

 packing or transportation boxes. Storage space for larger 

 apparatus and materials is afforded by a room to which entrance 

 is given by the doorway indicated in room 42. 



Finally, room 50 is the " animal living room " of the laboratory. 

 The floor of this room is water proof so that cages and aquaria 

 may be thoroughly washed and the floor flushed at need. In 

 this vivarium are set cages for a variety of vertebrates. At pre- 

 sent, the laboratory is supplied with cages especially designed 

 for mice, rats, guinea pigs, rabbits, cats, monkeys and birds. 



