170 ARBOREAL MAN 



5. With a monkey the effects of removal of the pictured 

 movement area are much more grave, for the animal is 

 very considerably damaged by the operation. It is not 

 completely, but it is partially paralyzed, and the paralysis 

 affects the hand movements far more than the leg move- 

 ments. There is still, however, a very well-marked 

 ca]3acity for recovery. 



6. In Man the effects of injury to, or disease of, this 

 area, or of the fibres coming from the area, are very well 

 known, and a Man whose pictured movement area is 

 entirely destroyed is completely paralj^zecl on one side 

 of his body. Moreover this paralysis is permanent. 

 This unilateral paralysis, or hemiplegia, is of a very 

 special type (upper neurone type), for the muscles them- 

 selves are perfectly capable of acting, are perfectly well 

 nourished, and in a good state of tone; but their move- 

 ments cannot be initiated for any pictured movement. 

 Now, in connection with this upper neurone t^^pe of 

 paralysis, there is one strange clinical fact which may be 

 expressed in the usual axiomatic manner, by saying that 

 " a muscle which can 2^^^'form two movements may he 

 paralyzed for one movement, and 7iot for the other '^ One 

 pictured movement centre may be damaged, while a 

 neighbouring one may be spared, and the muscle is only 

 deprived of its power to take part in one of its previously 

 possible movements. But more interesting still are those 

 cases in which a muscle is entirely paralyzed for all 

 pictured movements by the destruction of these areas, 

 for then the muscle may still act, j^rovided it plays some 

 part in any movement which is not represented in the 

 pictured movement area. 



For example, a muscle (M. trapezius) which acts upon 

 the shoulder and arm, and also upon the ribs, may be 

 quite unable to perform its pictured movements upon 

 the shoulder and the arm, after such a lesion (hemi- 

 plegia), but is quite competent to act when the patient 

 labours in respiration, coughs, or sneezes, these move- 



