194 JOSEPH DUEKSON STOUT 



The comparison of the extent of the motor field as demon- 

 strated by the present work, and the extent of the motor field 

 as demonstrated by the methods of Campbell, brings out the fol- 

 lowing differences. The motor field, as given by Campbell, is 

 bounded posteriorly by the ansate fissure. In the present work 

 the motor field extends farther posteriorly to the point where 

 the lateral fissure bends inward (sometimes outward). Camp- 

 bell's field then approaches the inner end of the crucial sulcus and 

 passes over onto the median surface of the hemisphere immedi- 

 ately posterior to the inner end of the crucial sulcus. In the 

 present tests motor reactions were obtained by the .stimulation 

 of the area between the angle of the lateral fissure and the 

 median line in many of the animals, although in a few the stimu- 

 lable area did not reach quite to the median line posteriorly. In 

 all animals there was a stimulable area internal to that portion 

 of the lateral fissure lying anterior to the ansate fissure. No 

 reactions were obtained from stimulation of the median sur- 

 face of the hemisphere, posterior to the crucial sulcus, except in 

 the case of cat 16, where a narrow stimulable area was found 

 immediately adjacent to the posterior bank of the opened crucial 

 sulcus. It did not reach to tne margin of .the hemisphere. Re- 

 actions were obtained from the stimulation of a narrow strip 

 of cortex within the median-line, anterior to the crucial sulcus, 

 though, according to the description of Campbell, the motor 

 area only extends to that portion of the median surface of the 

 hemisphere lying posterior to the crucial sulcus. Anteriorly and 

 laterally the extent of the motor field, as found in the present 

 tests, ^is identical with the extent mentioned by Campbell. 



MOTOR AREAS LYING WITHIN THE CRUCIAL SULCUS 



.The results obtained from the stimulation of the banks of the 

 crucial sulcus, either after separation by lifting the posterior 

 bank backwards or after the removal of the posterior bank, cor- 

 respond with those which have been described for the superficial 

 cortical areas. 



The difficulties encountered in the .investigation of the func- 

 tions of the banks of the crucial sulci are considerable, owing 



