590 PHYSIOLOGY CHAP. 



held that the motor zone of the cerebral cortex of , man has 

 approximately the same extent as that of the inferior apes, and 

 comprises both the central or Kolandic convolutions and the para- 

 central lobe and foot of the frontal convolutions. This view is 

 supported by positive and negative cases. Whenever there is 

 paralysis of voluntary movement of cortical origin, localised to 

 one half of the body, the post - mortem examination shows a 

 destructive lesion in this region of the opposite hemispheres, while 

 lesions of other parts of the cortex are not accompanied by any 

 obvious paralysis of voluntary movement during life. 



As regards the division of the human motor area into different 

 centres corresponding with the different muscular groups, clinical 

 observation agrees with the results of physiological experiment on 

 monkeys (Fig. 298). The paralysis of the muscles, the centre of 

 which has been destroyed, is usually complete, and diminishes in 

 adults less readily than in monkeys, showing that in man the 

 motor area is of more importance than in monkeys in the 

 execution of voluntary movements, just as it is more important in 

 monkeys than in dogs. In man, too, it can sometimes be shown 

 that a muscle which is incapable of carrying out any isolated 

 voluntary contraction preserves its power of acting in association 

 with other muscles. 



Contracture is seen more readily in man than in the monkey. 

 It consists in a state of hypertonus of the paralysed muscles, due in 

 all probability to suppression of the inhibitory impulses which the 

 spinal centres habitually receive from the cerebral cortex, while 

 the tonic influences constantly flowing to these centres from the 

 cerebellum persist. It can be seen in man, and to a lesser degree 

 in monkeys, that in hemiplegia from cerebral lesions exaggera- 

 tion of spinal reflexes is associated with contracture, while in 

 paraplegia from total transverse lesions of the cord contractures 

 never occur, and the spinal reflexes are diminished or abolished. 



So far the most reliable observers agree. But when it comes 

 to confirming by clinical and anatomo- pathological observation 

 the conclusions obtained from animals in regard to the localisation 

 of cutaneous and muscular sensibility in the cortex, there is 

 much controversy. 



In their first publications (1877-79) Charcot and Pitres cited a 

 series of cases of cortical motor paralysis in which cutaneous and 

 muscular sensibility remained perfectly intact. Tripier (1880) 

 was the first who maintained from his own clinical observations 

 that the motor area of the Kolandic region is at the same time a 

 sensory zone, because lesions of it produce disturbances of motility 

 and sensibility. Petrina (1881), Exner (1881), Lisso (1882), main- 

 tained the same view. In a subsequent clinical study (1883), 

 Charcot and Pitres opposed this tendency. While admitting the 

 force of the clinical facts adduced by Tripier and other observers 



