330 DISEASES OF THE NERVOUS SYSTEM. 



In any consideration of the nature and treatment of diseases 

 of this system, it ought ever to be remembered that the pri- 

 mary or such as seem to have their origin in the nervous 

 centres, and with which we are presently more particularly 

 concerned, are probably less numerous than those which may 

 be regarded as merely secondary or symptomatic, resulting 

 from diseases of other and different organs. 



These two varieties of nervous diseases will, as a rule, be 

 found evidencing themselves in a somewhat different manner. 

 In those cases where the nervous structures are primarily 

 affected, the earliest symptoms will be found associated with 

 perverted nerve-force : in the other, or where the interrupt^ 

 nerve-force is the result of some general or local disturbance, 

 the appearance of the symptoms connected with the nerve- 

 structures will be found to succeed or to appear synchronously 

 with those of the inducing affection. 



Although our knowledge of the entire nervous system, or of 

 any particular section of it, is even now far from complete, 

 either as to its inherent poAvers and activities, or its associa- 

 tions, and susceptibilities of acting, or being acted upon by 

 other orders of the animal system, we yet know enough, from 

 the results of direct experiment and careful clinical observa- 

 tion, to enable us to formulate certain elementary propositions, 

 which assist us in making diagnoses of affections of different 

 parts of this important system. 



Within certain limits, it must be remembered that the 

 ability to locahze diseases of the nervous system is absolutely 

 needful for anything like rational or successful treatment. 

 We have to recollect that its three great constituent portions, 

 the brain, the spinal cord, and nerves, may be separately or 

 conjointly affected with disease, and that to these associations 

 we must look for an explanation of many of the complex phe- 

 nomena so often exhibited. 



I. The earliest object of our examination in approaching 

 diseases affecting the nervous system is to determine whether 

 the affection is cerebral, spinal, or peripheral, or whether the 

 phenomena exhibited pertain to more than one localit}'. 



We presume the brain-substance proper to be chiefly in- 

 volved (a) when perception, volition, and special sensation are 

 affected ; (b) when motorial and sensory activity are affected. 



