chap, xv.] ELECTRICITY IN DIAGNOSIS. 161 



their higher centres, their lower being left intact, by 

 a lesion in the brain itself, or by a lesion in the cord 

 above the seat of their lower centres ; and in each of 

 these cases the lesion would be called central. If, 

 however, the lesion were to be in the cord affecting 



O 



the centre from which the nerves supplying the 

 muscles come off, or if it were to be in the nerves, 

 cutting off' communication between the cord and the 

 muscles themselves, it w T ould be called PERIPHERAL. 

 Thus central paralysis is dependent upon disease in 

 the brain, or in the cord, higher up than the place of 

 origin of the nerves for the affected muscles, while 

 peripheral paralysis is due to disease in the cord 

 affecting the centres connected with the paralysed 

 muscles, or to disease of the nerves ; and this would 

 include injury to the nerves, e.g. cutting, bruising so 

 as to deprive them of nervous continuity. 



Now, this being explained, the main fact, stated 

 broadly, is that nerves and muscles paralysed by a 

 central lesion have their irritability unaffected, while 

 nerves and muscles paralysed by a peripheral lesion 

 have their irritability rapidly diminished and finally 

 abolished. 



In the central lesion the nerves and muscles still 

 retain their connection with the centres in the spinal 

 cord. They are only removed from the influence of 

 the will, so that voluntary motion is in abeyance, but 



i " 



the nourishment of nerves and muscles remains, and 

 no sign of any impaired function ought, therefore, to 

 be present. Of course, volition being suspended as 

 regards them, their functions are no longer performed. 

 They fall into disuse, and since, in course of time, 

 enfeeblement always attends disuse, after an interval, 

 diminished irritability will be perceived. This is, 

 however, directly the result of disuse, and only in- 

 directly the result of the lesion. The irritability can 

 be restored by the use of faradisation, which affords 



