CENTRAL NERVOUS SYSTEM 



539 



animals (dog, etc.) ablation of the thalamus leads to immediate blindness 

 which, however, is soon replaced by psychical blindness only (Panizza, 

 1855) ; this demonstrates that a function resembling that of the cerebral 

 cortex is still to some extent retained. In man its connections are of an 

 extremely intricate kind since it forms the main relay-station of all the 

 tracts spreading upwards towards the cortex. Those parts which are 

 concerned particularly with the special senses are the lateral geniculate 



Neive II 

 Spiriform nucleus 



Basal optic ganglion 

 Brachium tectl 



Lat. geniculate body 



Xeotriatuni 

 Thalanio-cortical tract 



Thalamus 

 Nucleus rotundus 



TECTUM 



Nucleus lat. mesencephali 

 (torus) 



Ganglion isthmi 

 Nucleus semilunaris 



Lat. lemniscus 



VIII. Cochlear 

 VIII. Vestib. 



Nerve V 



Post, root ganglia 



FiCx. 714. — The Visual Pathw.\ys in a Typical Bikd. 



bodies (vision) and the medial geniculate bodies (audition and possibly 

 ec{uilil)ration) while the pulvinar has indirect visual and auditory associations. 



The ventral part of the diencephalon is occupied by the hypothalamus, a 

 collection of nuclei with rich intra-diencephalic connections which in the 

 higher Vertebrates are concerned with cardiac acceleration, elevation of the 

 blood pressure, the maintenance of the intra-ocular pressure, pupillary 

 dilatation, retraction of the nictitating membrane, pilo-erection, and 

 inhibition of the gut, as well as such vegetative functions as the regulation 

 of temperature, water, fat and carbohydrate metabolism, sleep and sexual 

 activity. 



The optic thalamus and its associated nuclei are primitive in Cyclo- 

 stomes, being chiefly concerned with olfactory, visual and visceral sensory 



