8 INTRODUCTION 



while up to that point he had stood bolt upright. Most 

 persons were not aware of this, because this change in 

 posture cannot be noticed from the front. I happened 

 to sit to the side and caught the movement every time. 

 It was the same that was noted by Dr. Miessner, an- 

 other member of the commission, (see page 256), but 

 concerning which he did not give me a more complete 

 account. Later I learned through Professor Th. W. 

 Engelmann that the very same movement was employed 

 not long ago, for giving signals to a dog exhibited at 

 Utrecht. This particular movement is very well adapted 

 to commercial purposes, since the spectator always tries to 

 view the performance from a point as nearly in front of 

 the animal and its master as possible, thus making the 

 detection of the trick all the more difficult. 



The details of the various experiments made by this 

 commission are given in an excerpt from the records 

 kept by Dr. von Hornbostel, which I showed to a small 

 group of persons a few days after the 12th of September 

 (Supplement III). At that time none of the particulars 

 was published, because the commission wished to wait 

 until some positive statement might be made. The public 

 was merely to be assured that a group of reputable men, 

 from different spheres of life, who could have no pur- 

 pose in hazarding their reputation, believed that the case 

 was one worthy of careful investigation. 



I left Berlin on September 17th and did not return 

 until October 3d. In the meantime Mr. Schillings con- 

 tinued the investigation, and was assisted in part by Mr, 

 Oskar Pfungst, one of my co-workers at the Psycho- 

 logical Institute. For the first time a number of tests 

 were now made in which neither the questioner, nor any 

 of those present knew the answer to the problem, i^ucli 



