CH. XLVIII.] SENSORI-MOTOK AREAS. 679 



left half of the field of vision ; the animal turns its head and eyes 

 to the same side as the lesion, or in technical language there is 

 conjugate deviation of head and eyes to the right. 



Stimulation of the visual area (and this is true for both the 

 occipital lobe and the angular gyrus) leads, no doubt, to a sub- 

 jective visual sensation of the corresponding halves of the two 

 retinae. Suppose the right visual area is stimulated, the subjec- 

 tive sensation will appear to come from the right halves of the 

 retina) ; the animal therefore imagines light is falling on its eyes 

 from the left, and so there is conjugate deviation of the head and 

 eyes to the left ; that is, the opposite side to that stimulated. 



The auditory area was localised by Ferrier in the superior 

 temporo-sphenoidal convolution. But there is considerable doubt 

 whether this is correct ; it is so much more difficult to tell when 

 an animal is deaf than when it is blind. Similar uncertainty 

 exists as to the situations for taste and smell. No doubt they are 

 closely connected, and they have been placed provisionally in the 

 uncinate convolution, and tip of the temporo-sphenoidal lobe. 

 The large size of these parts in animals with a keen sense of smell 

 lends support to this idea. 



Tactile sensibility was localised by Schafer in the limbic lobe, 

 but there is so much doubt about this, that a query is placed after 

 the words " tactile sense," in the gyrus fornicatus in fig. 503. 



Munk's view, supported in this country by Bastian, Mott, and 

 numerous others, is that the sensory fibres from the skin and 

 muscles terminate in the Rolandic area ; and the histological 

 researches of Golgi and Ramon y Cajal (see figs. 481 and 484) 

 point to the same conclusion. This is, in fact, what one would 

 expect ; volition and feeling are associated together so closely 

 physiologically, that anatomically we should expect to find the 

 commencement of the volitional fibres contiguous to the termina- 

 tions of the sensory fibres. That this is really the case has been 

 shown by a careful examination of the sensation in animals in 

 which the Rolandic area has been removed, and in cases of hemi- 

 plegia in man. A delicate test is to place a clip on the fingers 

 or toes, taking care the animal does not see the clip put on. If 

 there is loss of tactile sensibility the monkey either takes no notice 

 at all of the clip or removes it after a long delay. Whereas if sensa- 

 tion is perfect the monkey at once seizes the clip and flings it away. 

 It is found that the intensity of both the motor and sensory para- 

 lysis are directly proportional to each other. Hence the term motor 

 area, which we have been provisionally employing for the Rolandic 

 area, should be replaced by the more correct term sensori-motor 

 or kinsesthotic area. These new terms indicate that what really 



