SEC. 4. THE FUNCTIONS OF OTHER PARTS OF THE 



BRAIN. 



If the views just expressed are true then it is clear that the 

 proper method to study the brain is to trace out a cerebral 

 operation along its chain of events rather than to seek to attach 

 readily definable functions to the cerebral anatomical components. 



We may therefore be permitted to summarise very briefly what 

 can be fairly placed under this heading. 



Corpora Striata and Optic Thalami. These two bodies, often 

 spoken of as 'the basal ganglia/ are undoubtedly the great means 

 of communication between the cerebral hemispheres on the one 

 hand and the crura cerebri on the other. Though some fibres appear 

 to pass from the crura by or through the ganglia to the cerebral 

 convolutions without being connected with the nerve-cells of those 

 ganglia, the great mass of the peduncular fibres are probably con- 

 nected with the superficial grey matter of the hemispheres in an 

 indirect manner only, the lower or anterior fibres (crusta) passing 

 first into the corpora striata, and the upper or posterior fibres (teg- 

 mentum) into the optic thalami. This anatomical disposition would 

 lead us to suppose that these bodies have important functions in 

 mediating between the psychical operations of the cerebral convo- 

 lutions on the one hand, and the sensori-motor machinery of the 

 middle and hind brain on the other; and the separate courses taken 

 by the peduncular fibres would further lead us to expect that the 

 functions of the corpora striata differ fundamentally from those of 

 the optic thalami. 



When in the human subject a lesion occurs involving both 

 these bodies, on one side of the brain, the result is a loss of sensa- 

 tion in, and voluntary power over, the opposite side of the body 

 and face, a so-called hemiplegia, which may be absolutely complete 

 without any impairment whatever of the intellectual faculties. 

 The will and the psychical power to receive impressions are present 

 in their entirety, but neither efferent nor afferent impulses can 



