Functions of the Cerebrum. 631 



the brain, and from the sense organs, direct to the cortex, the Corpora 

 Quadrigemina, the Optic Thalamus, &c. , and direct efferent fibres run 

 from the cortex, the corpus striatum, &c. It has been proved by the 

 experiments of a dozen competent physiologists, that the motor nerve 

 fibres leading down from the cortex of the brain are special tracks of 

 stimulation between the cells of the cortex and particular muscles. For 

 after the cortex has been removed, and the stimulating galvanic elec- 

 trodes applied to the medullary fibres beneath, the same motor effects 

 are observed in the muscles of the limbs that would have taken place if 

 they had been applied to the cortical cells. These nerves ' ' stand to 

 the cortical matter precisely in the same relation as the anterior spinal 

 roots do to the anterior horns of the spinal cord." ( Ferrier.) This an- 

 alogy extends to the effects of disease in the two regions. ' ' When the 

 anterior horns of the spinal cord are diseased (as in anterior polio-my- 

 elitis), or the anterior roots are divided, the motor nerves, in the course 

 of four or five days, entirely lose their excitability, and undergo com- 

 plete degeneration." Likewise it was found that after the gray mat- 

 ter of the cortex was removed, the motor medullary fibres which were 

 at first excitable, in four or five days lost their excitability, and it has 

 been shown that after destruction of the cortex alone, degeneration 

 takes place not only in the fibres of the corona radiata, but in their con- 

 tinuations down the pyramidal tracts of the medulla oblongata and the 

 spinal cord. 



When the motor centers in the cortex of the cerebrum are destroyed, 

 such destruction is followed by degeneration of the pyramids in the 

 medulla oblongata, the degeneration taking place above the decussation 

 of the pyramids on the same side on which the cortical injury has taken 

 place, and on the opposite side below the decussation. This indicates 

 that the pyramids contain the motor fibres which carry the stimulations 

 made up in the cortex, including those constituting the will. 



I quote below from Carpenter's comments on the experiments of Dr. 

 Ferrier in stimulating the action of the brains of live animals by means 

 of an interrupted galvanic induction current which could be increased 

 or diminished at pleasure, and which was usually no stronger than could 

 be borne without much discomfort on the tip of the tongue. It was 

 commonly necessary to increase the strength of the current after the 

 partial exhaustion of the nerve fibres by continuous stimulation in any 

 one spot. But after such exhausted place was allowed to rest awhile it 

 would recover so that it could be stimulated again. Dogs, cats and 

 rabbits were operated upon and they were first chloroformed to render 

 them passive and unconscious. A part of the skull was then removed 

 so as to expose portions of the brain to view and the electrodes of the 

 coil were applied directly to the surface of the cortical matter of the- 



