534 W. T. JAMES 



commutator from the experimental room (see text-fig. 85, fig. 

 2). The speed of the commutator could be varied by placing 

 wheels of different diameters on the synchronous motor 

 operating it. In addition to the clicker, other auditory signals, 

 including a bell, buzzer and whistles, were used. All were 

 of the regular commercial type with no form of refinement. 



Tactile stimuli were presented by the same method as that 

 used by Pavlov. A cup containing a small balloon studded 

 with prickers (blunt metal points) was fastened to the skin 

 of the dog. When the balloon was expanded, the prickers 

 pressed against the skin. The mechanism was controlled from 

 the experimental room by means of an atomizer bulb and 

 tube. 



Olfactory stimuli were used with some of the best balanced 

 dogs. In most cases the odor of vanilla signalled the food. 

 The vanilla was enclosed in a bottle with one tube leading 

 from the bottle to the lower jaw of the animal, and another 

 to the experimental room. By placing air pressure on the 

 tube in the experimental room, the odor of vanilla was 

 presented. 



The specific motor response used in the experiments in- 

 volved the avoiding movement of the foreleg to an electric 

 shock. The electrodes were applied to the wrist. A Harvard 

 inductorium was used and the strength of the shock evaluated 

 in the units indicated on that apparatus. The complete avoid- 

 ing method was employed, that is, the dog avoided the shock 

 by breaking the circuit to the electrode when the leg was 

 raised. The circuit was broken by a sliding contact switch 

 activated by a string from the leg of the dog. A diagram of 

 this apparatus is shown in figure 3, text-figure 85. 



During the experiments, records of the reactions of each 

 animal were made on a kymograph. The record includes the 

 salivary and motor reactions, breathing changes, and head 

 movements. Typical graphs of each dog were photographed 

 for permanent records. 3 



3 The photographs of the records were made before the paper was fixed by 

 shellac. In this way all highlights were eliminated. Eastman process film was 

 used and developed in the high contrast developer D9. 



