178 Leyton and Sherrington 



members of the same group of elementary movements follow now in one 

 order, now in another, according as the point of cortex stimulated is 

 chosen now at one place or now at another not too far apart, and 

 influenced also by the stimulations that have been more immediately 

 precurrent. It is the isolated and restricted character of the primary 

 movements elicited by punctate stimulation of the cortex, or, to repeat 

 the term introduced above, their fractional character, which makes so 

 equivocal any purpose that an observer, who would interpret their purpose, 

 can assign to them. Such a movement as the extension of the index finger 

 can serve many purposes, so, again, a closure of the lips, or a retraction 

 of the tongue, or flexion of the ankle. Some of the facial movements 

 observed suggest mimetic acts, some the acts concerned with feeding ; 

 some, such as the narrowing of the glottis, might be mimetic on one 

 occasion, deglutitional on another. But the combinational sequences are, 

 so to say, eloquent of purpose in most instances. The large variety of 

 partial, though discrete and in themselves perfect, movements of separate 

 portions of the bodily framework, evocable b}^ localised point-to-point 

 stimulation of the motor cortex, and the multiform combinations which 

 these assume under cortical reaction and the rich mutual associations of the 

 cortical motor points which the physiological phenomena of " facilitation " 

 and " deviation of response " reveal, are suggestive. They lead to the sup- 

 position that from movements of locally restricted parts, e.g. movements of 

 a finger or of a limb-joint (movements themselves discrete and individually 

 separable in the motor cortex), the upbuilding of larger combinations varied 

 in character and serviceable for purposes of different and varied kind, 

 prehensile, defensive, locomotor, mimetic, masticatory, deglutitional, orienta- 

 tional (in von Monakow's (30) sense), etc., is one of the main offices per- 

 formed by the motor cortex. The functional properties of this cortex seem 

 specialised for that end. It appears at first sight surprising that a motor 

 nervous organ relatively so high as is the cerebral cortex in the nervous 

 hierarchy, where the power to deal with large integrated complexes of the 

 motor machinery might be expected, exhibits on actual examination a 

 representation, still more or less discrete, of relatively small and " partial ' 

 movements. And in the motor cortex this discrete " representation " of 

 small local items of movement, each highly co-ordinated with others yet 

 separably elicitable, instead of becoming less evident with ascent to the 

 higher types of hemisphere, becomes more so. Thus, it is more evident in 

 cat and dog than in rabbit, more evident in the macaque than in cat or dog, 

 in baboon than in macaque, in gibbon than in baboon, and in the chimpanzee, 

 orang, and gorilla than in gibbon. It would seem that in order to preserve 

 the possibility of being interchangeably compounded in a variety of ways, 

 successive or simultaneous, these movements must lie, as more or less dis- 

 crete and separable elements, within the grasp of the organ which has the 

 varied compounding of them. To draw an analogy merely illustrative, the 

 synthesis of the proteins of the body requires that certain metabolic organs 



