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A MANUAL'OF PHYSIOLOGY 



stimulation). For certain purposes the method of Ewald has 

 advantages. He fixes in a trephine hole in the skull an ivory plug, 

 through which pass the electrodes. When the animal has recovered 

 from the operation, the region of the brain in contact with the 

 electrodes can be stimulated without fastening the animal. 



'Motor' Areas.* These have been recently localized with 

 great care (both by stimulation and by removal of portions of 

 the cortex) in the brains of the higher apes (gorilla, orang, and 



chimpanzee) by Sher- 

 rington and Griinbaum, 

 and there can be no 



w x doubt that the results - 



li.L. 

 t 



f 



FIG. 350. DOG'S BRAIN WITH LESION. 



A portion of the cortex indicated by the shaded 

 area was destroyed by cauterization. The symp- 

 toms were complete blindness of the opposite 

 eye (in this case the right) ; weakness of the 

 muscles of the limbs and of the neck on the right 

 side ; slight weakness of the limbs on the left 

 side. When the animal walked, there was a 

 tendency to turn to the left in a circle. In 

 eating or drinking, the head was turned to the 

 left, so that the mouth was oblique, and the right 

 angle of the mouth was lower than the left. 

 The tail movements were normal, and there was 

 no deviation of the tail to one side. 



in their general outlines 

 at least, can be applied 

 to the human brain. 

 These observers em- 

 ployed the so-called uni- 

 polar method of stimu- 

 lation. 



The ' motor ' region 

 includes the whole 

 length of and the whole 

 of the free width of the 

 precentral or ascending 

 frontal convolution, and 

 dips down to the bottom 

 of the central sulcus (fis- 

 sure of Rolando in 

 man), but does not ex- 

 tend behind the sulcus. 

 It extends also into the 

 depth of the fissures, so 

 that the hidden part of 

 the excitable area prob- 

 ably equals, perhaps ex- 

 ceeds, the part which 



is free on the surface of 

 the hemisphere. The anterior limit of the ' motor ' field is not 

 quite sharp, but shades off somewhat gradually into inexcitable 

 cortex. The sulci in this region cannot be considered to repre- 



* Since the so-called 'motor' area, as is now well known, is really 

 sensori-motor, and a region having to do purely with the discharge of 

 motor impulses does not exist, it would be better to call it the sensori- 

 motor, or, following Bastian's suggestion, the kinsesthetic area. Probably, 

 however, the alteration of a term so long sanctioned by custom in physio- 

 logical writings would lead to confusion. Accordingly, in what follows 

 the word ' motor ' will be retained, but to show that it is used in a special 

 sense it will be enclosed in quotation marks. 



