2^6 THE GROWTH OF THE BRAIN. 



so doing really hamper further advance. The partial 

 character of the explanations which are to be given 

 should therefore be kept in mind. 



The tracts connecting the hemispheres with the spinal 

 cord, and bearing incoming impulses, run mainly 

 through the dorsal portions of the central axis. On 



FIG. 53. Schema of the projection fibres within the brain (Starr.) 

 Lateral view of the internal capsule. A, tract from the frontal 

 gyri to the pons nuclei, and so to the cerebellum ; B, motor 

 tract ; C, sensory tract for touch (separated from B for the 

 sake of clearness in the schema) ; D, Visual tract ; E, auditory 

 tract ; F, G, H, superior, middle, and inferior cerebellar 

 peduncles ; J, fibres from auditory nucleus, the inferior quad- 

 rigeminal body ; K, motor decussation in the bulb ; Vt, fourth 

 ventricle. The numerals refer to the cranial nerves. The 

 sensory radiations are seen to be massed towards the occipital 

 end of the hemisphere. 



passing from the brain stem into the hemispheres these 

 tracts, in company with other fibres bearing incoming 



