76 K. S. LASHLEY AND S. I. FRANZ 



convexity of the cerebrum to the formation and retention of 

 habits which involve chiefly responses to tactile and kinesthetic 

 stimulation. After operation to destroy the frontal pole of 

 both hemispheres (section III) or the entire dorsal convexity 

 of the cortex (section V) the animals were trained on the in- 

 clined-plane box or maze and their rate of learning was compared 

 with that of normal individuals. In other experiments (sections 

 I, II, and IV) normal animals were trained upon the same prob- 

 lems and after the destruction of various areas of the cortex were 

 tested to determine the degree of retention of the habits pre- 

 viously established and their ability to reform the habits in the 

 cases where these had been lost. 



In the carrying out of the operative procedures excessive 

 hemorrhage was not infrequently encountered. To avoid this 

 as much as possible the operations were performed rapidly. 

 The sizes of the brain and skull are such that there is no space 

 for packing to check a hemorrhage, and it was thought best to 

 operate quickly even if some animals died because of the result- 

 ing hemorrhage from the cerebral lesion, rather than have an 

 equal or greater number of deaths from hemorrhage from the 

 longitudinal sinus. This was possible because of the number of 

 animals which were available. Most of the cerebral operations 

 were carried out through small skull openings, and partly be- 

 cause of this the lesions differed in all cases. Slightly different 

 positions of the heads of two animals make the views of the small 

 operative fields dissimilar, variations in the sharpness of the 

 section knife make distinct variations in the ease, depth and 

 completeness of the intended sections, and even slight variations 

 in the relations of the brain to the skull sutures give difficulties 

 that are not easily overcome. The complete removal of the 

 top of the skull and the consequent full view of the superior 

 surface of the brain would have been a more satisfactory pro- 

 cedure in some ways. The difficulty of controlling the hemor- 

 rhage from the skull is however added to the difficulty of con- 

 trolling the hemorrhage from the cerebral section. At the same 

 time even though the top part of the skull be removed without 

 any ill effect other difficulties persist. The point of insertion of 



