In order to ascertain the possibility of structural regeneration in the cortical areas of the cerebral hemispheres, the cortex of the sigmoid convolution was extirpated in puppies aged 10 and 14 days. These animals were then sacrificed 2 and 7 months after the operation. Their brains were fixed in 10% formalin and sections of the material were stained with cresyl violet. The site of the defect was clearly visible macroscopically. However, its size was considerably less than at the time of the operation. Due to growth of the brain, the edges of the injured area moved over the defect, closing it over and joining each other. This was quite distinct microscopically. However, where the size of the injury was enlarged by hematoma and reached the lateral ventricle, no closing in of the tissue or juncture of the edges was observed. Thus, in the opinion of the author, there was no replacement of the brain matter by new matter, but there only occurred superposition and juncture of the adjacent areas, which created the appearance of tissue regeneration.