144 Journal of Comparative Neurology. 



with the cerebellum. Certain of its (intermediate) cells send 

 their fibers into the cerebellum. These cells are most numer- 

 ous where the nerve specially concerned in equilibration comes 

 in ; they are next in number in the segments of the lower part 

 part of the back (columns of Clarke) and in the external nu- 

 cleus of Burdach. All the fibers end near the surface of the 

 cerebellum, where the coordination elements of all the segments 

 are brought near one another. The cerebellum then contains 

 cells which influence directly or indirectly the motor elements 

 of the various segments, and establish the necessary coordina- 

 tion. The neurones which have their cell-body in the segments 

 and their fiber arborization in the cerebellum, are called afferent 

 cerebellar neurones ; the ones which have the cell-body in the 

 cerebellum and the fiber arborization in the segments, efferent 

 cerebellar neurones. 



The supersegmental part of the mid-brain, on the main 

 the corpora quadrigemina, has a great number of afferent neu- 

 rones; in lower animals almost every segment sends fibers to 

 meet the optic apparatus in the mid-brain ; but in man the 

 afferent mid-brain neurones are limited largely to the auditory 

 segment (lateral fillet) and few fibers of Gowers' bundle (Mott), 

 Eferent neurones of the mid-brain are not known with certainty 

 (see however Bechterew^). 



The most important extrasegmental mechanism is however 

 that which grows up between the olfactory and the optic seg- 

 ments. We know it as cerebral cortex and basal ganglia, or 

 cerebral mechanisms. Here too we find affere?it neurones from 

 each segment of the neural stem. These neurones are how- 

 ever already 'centralized. ' It is commonly known that the affer- 

 ent cerebral fibers for the spinal segments have their cells 

 grouped together in the Nuclei of GoU and Burdach, at the 

 point where the head segments go over into those of the neck. 

 The peripheral sensory cells of the more caudal segments send 

 their fibers all the way to meet them ; they form the posterior 



1 W. Bechterew, Uebcr centrifugale aus der Seh- uiid Verhiigelgegend aus- 

 gehenden Riickenmarksbahnen. Neur. Centralbl. No. 23, 1897. 



