326 THE NERVOUS SYSTEM 



its connection with the cerebrum of the opposite side and 

 with the vestibulo-spinal tract of the same side it steadies 

 the vohmtary impulses from the cerebral cortex. 



In any reaction of the body the part which the proprio- 

 ceptive system plays is always secondary. An external 

 stimulus causes a certain motor response. This motor 

 response stimulates the proprioceptive nerve-endings. 

 It is the proprioceptive system which the cerebellum 

 dominates. 



Summary of Functions of the Lower Centres 



The corpus striatum, composed of the lenticular and caudate 

 nuclei, is said to contain a centre for heat- regulation (p. 251). 



The optic thalamus is believed to be the centre for the reception 

 of crude afferent sensations. It is in contact with nearly all sensory 

 nerves, especially with those from the eye, and with the cortex 

 cerebri. 



The red nucleus in the mid-brain is the head of the rubro- 

 spinal system. It is connected also with the cerebellum. 



The pons is a junction between one cerebral hemisphere and the 

 opjOTsite lobe of the cerebellum. 



In the medulla are the vaso-motor and respiratory centres. It 

 contains the nuclei of the vagus and hypoglossal nerves. Here 

 enters also the eighth nerve. The nucleus of Deiters comiects the 

 cerebellum, the vestibular nerve and the spinal cord. 



The function of the olive is unknown. 



