THE NEOPALLIUM. 349 



in the nuclei of the pons. Those fibers which pass through the 

 pons form in the medulla oblongata the well-known pyramidal 

 tracts. From these, fibers are given oft" to the motor nuclei of the 

 IX, X and XII nerves and at the posterior end of the medulla 

 oblongata the two tracts enter into the pyramidal decussation. 

 The decussation is not complete but the smaller part of the fibers 

 continue into the cord on the same side, forming the ventral 

 cerebro-spinal fasciculus. The crossed fibers together with a 

 small number of the uncrossed fibers form the lateral cerebro- 

 spinal fasciculus. Both of these bundles decrease in size as they 

 descend the spinal cord, the ventral bundle being used up in the 

 cervical and thoracic region and the lateral bundle gradually 

 diminishing but extending even into the sacral cord. The fibers 

 end in relation with the motor neurones of the spinal ner^•es. 

 Part of the fibers of the ventral bundle cross to the opposite side 

 and since the lateral bundles also contain uncrossed fibers it 

 is probable that throughout the whole length of the spinal cord 

 there are both direct and crossed connections of the cerebral 

 cortex with the motor nerves. 



6. The areas of association. When the areas which have 

 been described are myehnated there remains two-thirds of the 

 cortical area without myelinated fibers. At the same time the 

 projection tracts of the cerebral cortex seem to be fully formed. 

 Although it is quite possible that a certain number of projection 

 fibers may receive their myelin after this time and that some of 

 such fibers may be connected with parts of the cortex not included 

 in the above areas, it is clear that these are the supreme projection 

 areas of the cortex. Although the method of Golgi and the 

 degeneration methods give evidence that projection fibers arise 

 from the whole cortex, the method of Flechsig is the more rehable 

 for this question and it must be regarded as clearly estabhshcd 

 that the number of projection fibers connected with other parts 

 of the cortex is small compared with the number connected with 

 the senso-motor areas above described. 



The remaining two-thirds of the cortex is intercalated between 

 the several senso-motor areas so that each of them is separated by 

 a considerable space from the others. This whole area constitutes, 



