CHAPTER XLV. 



SPOEADIC J) IS'EASES— continued. 



LOCAL T)l&EA?>^8— continued. 



(H.) PAEALYSIS. 



Palsy or paralysis may be seen in various forms rather as a 

 symptom of a lesion than as a disease itself, the term palsi/ or 

 paralysis being commonly restricted to that form where motion 

 is lost, while the term anaesthesia implies a palsy of the nerves 

 of sensation. 



In order to understand the various lesions which may cause 

 paralytic symptoms, it is advisable that a glance at the physi- 

 ology of the spinal cord should now be undertaken. 



1. The spinal nerves have two roots ; and Sir Charles Bell 

 proved that the anterior (inferior in the lower animals) conduct 

 the power of motion, whilst the posterior (superior) are devoted 

 to sensation only. At one time it was thought that if the 

 corresponding columns of the cord were cut or injured, loss of 

 sensation only would result when the superior columns were cut, 

 and loss of motion if the inferior were cut across; but such 

 is not actually the case, for it has been demonstrated that if the 

 posterior columns are cut across, the result is not numbness 

 and insensibility, but hyperesthesia and loss of co-ordinating 

 power in the parts posterior to the section, with some local 

 pain, due not to any sensitiveness in the columns themselves, 

 but to the cut having traversed through the posterior roots of 

 the nerves. The same results are obtained if the restiform 

 bodies and small superior pyramids are divided, and as these 

 parts are connected with the cerebellum, and the superioi 

 columns of the cord, tlie deduction is, that the channel wliich 



