4 S. I. FRANZ AND K. S. LASHLEY 



but not after the removal of other parts, or if they can retain 

 but can not acquire habits after certain cerebral destructions, 

 there will exist a basis for further extensive and intensive work 

 on the so-called higher animals. The present work was under- 

 taken with these objects in view. 



Several questions were posed, although the facts to answer 

 only a few parts of these questions are now available. Some 

 of the questions are: Do rats retain habits of recent formation 

 after the destruction of certain cerebral regions? Do they re- 

 tain habits of long standing, or those in which there has been 

 an overtraining or over-learning? Can rats learn after the 

 removal of the whole cortex? If learning and retention are 

 possible after destruction of parts of the cortex, how much and 

 what parts of the brain are necessary for, 'and what parts are 

 normally used in the formation and the retention of habits? 

 At the present time there are available results of experiments 

 in which the frontal portions of the brain have been destroyed, 

 and in which there have been destructions of two-thirds or 

 more of the whole cortex (that of the cerebral convexity), but 

 only those experiments dealing with the effects of frontal de- 

 structions will be reported here. 



When the experiments were undertaken there was available 

 a large number of rats which has been trained in a simple maze 

 for other purposes and it was decided to use them in preliminary 

 tests. The maze was built after the pattern of the Yerkes dis- 

 crimination box (fig. 1). It consists of a starting compartment 

 (a) leading by a sliding door to a central alley (6), which at its 

 outer end offers the alternatives of the cul de sac (c) and the alley 

 (d) leading directly to the food (e). A maze of this character 

 had decided advantages for the training of large numbers of 

 animals but is not altogether suitable for tests on retention on 

 account of the speed with which it is learned and the degree of 

 probability that any given correct trial is the result of chance. 

 Incidental observations on the behavior of the animals in the 

 maze are therefore of great importance for the determination of 

 the retention of the habit. 



Two activities of the animals in the maze are to be especially 



