In order to resolve the conflicting results secured by various investigators of the possibility of conditioning leg withdrawal in spinal dogs sensitive pneumatic recording techniques and a procedure closely similar to that used by Shurrager and Culler, who had previously reported positive results, were employed. By administering long series of conditioned stimuli before application of the first unconditioned stimulus it was established that a "muscle-twitch" could be elicited with great regularity; this response did not differ in any respect from the response recorded after paired presentation of the conditioned and unconditioned stimuli. It was found that the frequency of occurrence of the response was a direct function of the intensity of stimulating current employed. "It is the view of the present writers that this phenomenon cannot be considered as conditioned or learned, in any sense of the word. Socalled 'conditioning' or 'extinction' curves obtained from spinal animals by this method are undoubtedly the result of some uncontrolled or unknown variable." (PsycINFO Database Record (c) 2006 APA, all rights reserved)