HABIT FORMATION IN THE DOG 33 



4. Position of the animal ivhen the stiniiilns is given. This 

 should also be the same for all stimuli — or as nearly the same 

 as is possible. I have already referred to a control-test of my 

 own which illustrates the value of this precaution. This condi- 

 tion mav be met by the use of the stimulus-cage which I have 

 devised, a cut of which appears on page 32. The explanation 

 of the sketch is as follows : A is the home-box, 4' x 4', in which 

 the animal is placed between stimuli, entrance being made from 

 without by the door V; B is an introductory alley, 6' long and 

 2' wide, leading to the alleys D and D'. These alleys are each 

 10' long and open to alleys E and E', which are shut off by the 

 two doors X and X'. These doors, as appears in the cut, are 

 made to open from the animal, and are closed automatically 

 by a small coiled spring. Each is pro^•ided with an iron lift 

 latch, which should be heaw enough to catch when the door 

 is closed without attention from the operator. A string is fast- 

 ened in a small hole drilled in the end of the le\-er of each of 

 these latches, and run through an eye-screw in the door above, 

 then through a pulley attached to the side of alley E or E' as 

 the case may be, then to the operator's place, so that by pulHng 

 the string the door may be unlatched and pulled open without 

 the operator's leaving his place. When the string is released 

 the door closes and latches itself. Alleys E and E' open into 

 two food-compartments F and F'. The covering of these boxes 

 is provided with two doors, located near the end of alleys E 

 and E', through which food is dropped. Y and Y' are two doors 

 opening from food-compartments F and F' into the home-box 

 A. These doors are not provided with latches, as they close 

 behind the animal, flush with the jambs, and cannot be opened 

 by an animal which has not free use of its hands, such as has the 

 monkey, raccoon, or the squirrel. They are provided with coiled 

 springs, like those on doors X and X'. My animals would usually 

 open these doors from the food-compartments, merely pushing 

 their way into the home -box, but it is well to pro\'ide a means 

 of opening them with strings as are doors X and X', for the 

 sake of timid animals. Door W is opened by means of a spring, 

 as doors X, X', Y and Y' are closed. A heavy gut cord is fast- 

 ened to an eye-screw near the top of door W. and run through 

 a small hole near the top of the outside frame-work of home-box 

 A, to the operator's station, where it is hooked until door W 



