PART IX. 

 DISEASES OF THE NERVOUS SYSTEM. 



CHAPTER I. 

 DISEASES OF THE BRAIN. 



General Considerations. Diseases of the central nervous 

 system are usually, for the purpose of convenience and 

 pedagogy, classified into those affecting the encephalon or 

 brain, those affecting the spinal cord, and those affecting 

 the peripheral nerves. 



This seems to be a logical classification, and this method 

 will be followed in presenting the diseases of the nervous 

 system. In order to correctly diagnose diseases of this 

 system, a knowledge of its functions as well as the seat of 

 each function is required. These will, therefore, be con- 

 sidered briefly. 



Preliminary remarks on the functions and seat of each: 



Cortex. The cortex of the cerebral hemispheres is the 

 seat of all psychic function, such as thought, the will and 

 sensation, and all efferent nerve fibers originate here. The 

 voluntary motor fibers also originate in the cortex, pass 

 through the pons to the medulla oblongata where they 

 cross to the opposite side and communicate with the motor 

 nerves of the extremities. All sensory nerve fibers and 

 fibers of special sense which conduct perceptible impulses 

 to the brain terminate in the cortex. The cortex of the 

 cerebrum, then, being the seat of the mind and of voluntary 

 movement, it follows that any destructive process affecting 

 this portion of the brain will produce psychic or mental 



