114 K. S. LASHLEY AND S. I. FRANZ 



elusive evidence that the cerebrum is or is not necessary for habit 

 formation. Burnett (4) failed to get decerebrate frogs to learn 

 a simple maze but it is possible either that the operation resulted 

 in such a disintegration of the animal's other habitual reactions 

 that the incentive for learning the maze was no longer adequate, 

 or that the maze presented a too complex habit and that a 

 simpler habit might still have been acquired. The experiments 

 certainly do not justify the author's sweeping conclusion that 

 learning is not possible in the absence of the cerebral cortex. 

 The statement in the introduction that learning is possible in 

 the decerebrate frog is based upon unpublished results on the 

 facilitation of the crossed reflex of the hind leg. 1 Goltz (5) 

 made an attempt to train his decerebrate dog but gave up quickly 

 for fear that the training methods would result in the animal's 

 death. Rothman (6) reported the acquirement of new motor 

 coordinations in his decerebrate dog but gave no details of the 

 experiment. It is not possible to be certain that the changes 

 in behavior noted by these authors were not concomitants of 

 recovery from operative shock rather than true examples of 

 habit formation. 



It may be that no complex habits are acquired in the absence 

 of the cerebral cortex but a fundamental point in the problem 

 of the physiology of learning is involved in the possibility of the 

 formation of simple habits wholly by the mechanisms of the 

 spinal cord and brain stem. Is there any fundamental difference 

 between the organization of the cerebrum and that of lower 

 centers such as to give the former special functions which are 

 lacking to the more primitive portions of the nervous system, 

 or are the cerebral and spinal functions alike save for the possi- 

 bility of greater complexities of reflex connections within the 

 cortex? Failure or success in obtaining habit formation in 



1 Some may object to. this as an example of learning, but it is undoubtedly 

 true that any modification of an animal's behavior due to repeated stimulation 

 (exclusive of fatigue phenomena) is properly called learning. The distinction 

 between " associative memory" and other types of acquired reactions is by no 

 means so clear as the exponents of this as a criterion of consciousness would 

 have us believe. 



