264 THE NERVOUS SYSTEM 



with fibers which, following the same course downward, are found 

 in the pyramidal tracts of the cord. All fibers passing from 

 these cortical areas mentioned through the internal capsule 

 occupy the anterior two-thirds of the posterior division of that 



FIG. 83. Scheme of the projection fibers 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 (sepa- 

 rated from B for the sake of clearness in the scheme); D, visual tract; E, auditory 

 tract; F, G, H, superior, middle, and inferior cerebellar peduncles; J, fibers between 

 the auditory nucleus and the inferior quadrigeminal body; K, motor decussation in 

 the bulb; At, fourth ventricle. The numerals refer to the cranial nerves. The sen- 

 sory radiations are seen to be massed toward the occipital end of the hemisphere. 

 (Am. Text-book.) 



tract. Furthermore, fibers from the posterior cortical area pass 

 through the posterior one-third of the posterior division of the 

 internal capsule to the optic thalamus, from which fibers pass 

 through the tegmentum to the pons and medulla and are continu- 

 ous with fibers from the sensory tracts of the cord. The decus- 

 sation of all these fibers has been mentioned. 



Fig. 84 taken in conjunction with Fig. 77 illustrates the most 

 recent ideas of the motor and sensory connections between brain 

 and cord and the motor and sensory paths in the cord. 



