3 8 THE NERVOUS SYSTEM 



Those fibres which do not take part in the decussation of 

 the pyramids pass downwards in the anterior funiculus of the 

 spinal medulla (Fig. 25), forming the direct or anterior 

 pyramidal tract. It is probable that all these fibres cross the 



Corpus callosunv- 

 Caudate nucleus- 



Thalamus^"" 



Motor fibres in internal'"" 

 capsule 



Decussation of 



pyramids 



- Island (of Reil) 



Lentiform nucleus 



Medulla oblongata 



FIG. 22. Diagram of Frontal (Coronal) Section of Right Cerebral 

 Hemisphere and Brain-Stem, showing the path of the Motor Fibres. 



In addition to the decussation of the pyramids, the numerous smaller decussations in 

 connexion with the motor cerebral nerves are indicated in the diagram. 



median plane at various levels in the spinal medulla and that 

 they terminate in the same way as the fibres of the crossed 

 pyramidal tract. 



In addition to the decussations which have just been de- 

 scribed, numerous smaller decussations occur at a higher level. 



