37G 



PHYSIOLOGY 



prolongation forwards of the tegmentum of the cms. This is often spoken 

 of as the subthalamic region. The red nucleus is a conspicuous object in 

 sections through the back part of this region, but gradually diminishes as we 

 proceed forwards, and disappears before the level of the corpora mammillaria 

 is reached. The mesial fillet, which in the mid-brain lies on the lateral and 

 dorsal aspect of the red nucleus, is prolonged upwards together with fibres 

 from the superior cerebellar peduncle into the ventral part of the thalamus, 

 where probably all of the fibres end in connection with the thalamic cells. 

 The substantia nigra gradually disappears. Before it has disappeared we 

 may see on its outer side a special collection of grey matter called the nucleus 

 of Luys or the corpus subthalamicum. In addition to the anterior and 

 posterior commissures already described as connecting the two optic thalami 

 at the front and back of the third ventricle, the two sides are connected about 

 the middle of the cavity by the middle or soft commissure. The optic 

 thalamus is often described together with the corpus striatum as forming 

 the basal ganglia. The corpus striatum is however genetically, and 

 probably functionally, part of the cerebral hemispheres, and its connections 

 will therefore be best dealt with when describing the latter bodies. 



THE AXIAL GREY MATTER 



In the spinal cord we could distinguish between the anterior grey matter 

 giving origin to the motor nerves, the posterior grey matter serving as an end 



LIGULA 



VAGUS] 



"ARCUATE 

 NUCLEUS 



XII. 



[HYPOGLOSSAL] 



Fio. 191. Cross-section of medulla showing nuclei of nerves x and XII. 

 (CUNNINGHAM.) 



station for a number <>i tin- sensory posterior root fibres, and a lateral horn, 

 less well marked, probably giving origin to the visceral system of nerves. 

 A- the central canal widens out to form the fourth ventricle, the relative 



