LOCALIZATIOX OF NERVOUS DISEASES. 331 



generally longitudinally and on one side — hemiplegia ; (c) when 

 muscles belonging to the face and tongue are similarly dis- 

 turbed ; {d) in some rare instances when motorial disturbance 

 occurs in a transverse manner — paraplegia ; (e) when certain 

 changes discoverable with the ophthalmoscope are observed 

 in the eyes. 



The spinal cord is regarded as the seat of disease {a) when 

 disturbance of motorial and sensory activities are located in a 

 bilateral or transverse manner — paraplegia — the spasm or para- 

 plegia varying according to the extent of cord cut off from 

 normal connection with the brain, the functions of which are 

 unimpaired ; (6) when the functional activity of bladder or 

 rectum is interfered with, indicated by retention of urine and 

 its consequences, or incontinence. 



Peripheral nerves are presumed to be diseased when the 

 phenomena of disturbance are confined to a particular muscle 

 or group of muscles, or to a restricted sensory surface. In 

 this way, either motion or sensation, according to the character 

 of the nerve-cord or both, may be impaired. Phenomena of 

 this latter character, it may also be recollected, exhibit them- 

 selves Avhen disease of nervous centres of a restricted character 

 exist. 



2. Further than this general association of clinical phe- 

 nomena with diseased states of the different parts of the 

 entire nervous system, we may in many instances, notwith- 

 standing many difficulties and conflicting opinions, Hnk the 

 symptoms exhibited with particular lesions of distinct areas 

 of the different centres. 



a. In the brain, allowing certain exceptions, we may regard 

 it as tolerably certain (1) that a lesion of one hemisphere is 

 represented by motorial disturbance of the opposite side of 

 the body ; (2) that particular injury to the cerebral cortical 

 matter will issue, according as this injury is irritative or de- 

 structive, in excitation or paralysis of those movements of a. 

 conscious or voluntary character ; (3) that disturbance, abnor- 

 mal activity, or depression of such movements as are auto- 

 matic or responsive, are indicative of, or wiU follow, irritative 

 or destructive interference with centres deeper seated than the 

 cortex. 



Of diseases of the cerehellum, we are in greater uncertainty. 



