CHAPTEE H. 



MOTOR AND SENSORY NERVES. 



Distinct seat of the motor and sensory properties of the spinal nerves Specu- 

 lations of Alexander Walker Views of Sir Charles Bell regarding the func- 

 tions of the anterior and posterior roots of the spinal nerves Experiments 

 of Magendie on the roots of the spinal nerves Properties of the posterior 

 roots of the spinal nerves Influence of the ganglia upon the nutrition of 

 the posterior roots Properties of the anterior roots of the spinal nerves 

 Recurrent sensibility Mode of action of the motor nerves Associated 

 movements Mode of action of the sensory nerves Sensation in amputated 

 members. 



THE physiological property of nerves which enables them 

 to conduct to and from the centres the impressions, stimulus, 

 force, or whatever the imponderable nervous agent may be, 

 is one inherent in the tissue itself, belonging to no other 

 structure, and is dependent for its continuance upon proper 

 conditions of nutrition. So long as the nerves maintain these 

 conditions, they retain this characteristic physiological prop- 

 erty, which is generally known under the name of irritability. 



Aside from the special senses, the sense of temperature, 

 and of weight, it is known to every one that through the 

 nerves we appreciate what are called ordinary sensations, 

 and are enabled to execute voluntary movements. If a 

 nerve distributed to a part endowed with sensation and the 

 power of motion be divided, both of these properties are 

 lost, and can only be regained through a reunion of the di- 

 vided nerve. Again, it is equally well known that if such 

 a nerve be exposed in its course and irritated, violent move- 

 ments take place in the muscles to which it is distributed, 

 and pain is appreciated, referred to parts supplied from the 



