206 PRINCIPLES OF PHYSIOLOGY 



ing complicated convolutions. These convolu- 

 tions constitute an immense web of grey matter 

 showing numerous neurones of a peculiar 

 pyramidal form, arranged more or less in 

 layers. Numerous fibres pass in all directions 

 connecting one part of the cerebral mass with 

 the other. All the structural details indicate 

 co-ordination of function. Thus the convolu- 

 tions are connected by many associational 

 fibres ; fibres pass from the anterior to the 

 posterior parts of the cerebrum ; and numerous 

 fibres form the great transverse commissure, 

 known as the corpus callosum, which connects 

 one hemisphere with the other. Other smaller 

 transverse commissures exist. The cerebrum 

 receives nervous impulses from all parts of 

 the body. The sensory tracts in the cord 

 send numerous fibres upwards, and these reach 

 the grey matter of the cerebral convolu- 

 tions, in the posterior and lateral regions, 

 forming arborizations or networks near motor 

 neurones that lie in layers in the grey matter, 

 more especially in certain convolutions on 

 the lateral aspect of the cerebrum, From these 

 motor neurones fibres (axons) pass downwards 



