THE CEREBRUM. 505 



areas are primarily sensor and secondarily motor, and therefore 

 should be termed sensori-motor. In Flechsig's own terminology 

 each cortico-petal or afferent tract is accompanied by a cortico-fugal 

 or efferent tract. 



In this view sensations, or the mental processes the outcome of 

 sensations, are the immediate cause of the movements of the mus- 

 cles connected with both the sense-organs and skeletal structures. 

 Though this interpretation viz., the coincidence of sensor and 

 motor areas appears more in accordance with the facts than the 

 earlier view, it must be admitted that there are many facts both of 

 a physiologic and pathologic character which it is difficult to har- 

 monize with it. 



The Motor Area of the Chimpanzee Brain. In a series of 

 experiments made by Sherrington and Griinbaum on the brain of the 

 chimpanzee it was discovered that the so-called motor area was not 

 so widely distributed as in the monkeys generally, but was confined 

 almost exclusively to the convolution just in front of the fissure of 

 Rolando, as it was impossible to obtain any movement on direct 

 stimulation of the convolution just behind it. All points on the 

 surface of the pre-central convolution, including the portion forming 

 the wall of the Rolandic fissure itself, were found to be excitable 

 and productive of movement when stimulated. The sequence of 

 representation from below upward is similar to that observed in the 

 monkey. One peculiarity, however, was the location of the area 

 for conjugate deviation of the eyeballs to the opposite side. This 

 is situated far forward in the middle and inferior frontal convolutions, 

 and separated from the areas in the pre-centra? convolution by a 

 region apparently inexcitable. These facts are of great interest and 

 value in the assignment of the motor areas in the cortex of the human 

 brain, as in its development and configuration the chimpanzee brain 

 more closely resembles the human brain than does the monkey's. 



The Localization of Motor and Sensor Areas in the Human 

 Brain. The observation of clinical symptoms and their interpreta- 

 tion by postmortem findings, the phenomena observed during surgical 

 procedures, and the results of embryologic investigations, point to the 

 conclusion that corresponding areas both for movements and sensa- 

 tions exist in the cerebral cortex of the human brain, though it^ is 

 probable that their locations do not in all respects coincide with 

 those characteristic of the monkey or even the ape brain. In the fol- 

 lowing diagrams (Figs. 226 and 227), the motor and sensor areas 

 are at least provisionally located, in accordance with recent obser- 

 vations. They are represented as limited or bounded by a serrated 

 line to indicate, as suggested by Mills, that they are not sharply 

 defined, but that they interfuse or interdigitate with surrounding 

 regions. 



