THE MAMMALIAN NERVOUS SYSTEM 81 



Sylvius, after which they end in or near the red nucleus (nucleus 

 ruber) under the superior colliculus. The superior peduncle 

 also contains ascending fibers from the spinal cord (ventral 

 spino-cerebellar tract of Gowers). 



Between the superior peduncles is stretched a thin sheet of 

 nervous tissue, the anterior medullary velum. This contains 

 nerve-fibers from the tectum or roof of the corpora quadri- 

 gemina to the cerebellum, the tecto-cerebellar tract. 



97. Inferior olives, pontile nuclei, arcuate nuclei, substantia 

 nigra. — These gray centers of the brain stem are all functionally 

 related with the cerebellum. All of these nuclei (except perhaps 

 the arcuate) send fibers to the cerebellar hemisphere of the op- 

 posite side (see Strong ('15)). Identify all of these nuclei and 

 enter them in the sketches. The cerebellar connections of the 

 inferior olive (olivo-cerebellar tract, see Herrick ('15), Figs. 72, 

 83 and 87) and of the pontile nuclei (brachium pontis, see Herrick 

 ('15), Fig. 87) should also be identified and indicated on the 

 sketches. The inferior olives and arcuate nuclei receive in- 

 ternal and external arcuate fibers from the sensory nuclei of 

 the oblongata. The inferior olive receives also a strong tract 

 from the thalamus (central tegmental tract) and a smaller 

 tract from the spinal cord (spino-olivary tract, see Herrick ('15), 

 Fig. 87). These cannot be easily distinguished in the sections. 

 Its chief discharge path is the olivo-cerebellar tract and a smaller 

 one (the olivo-spinal tract) discharges into the spinal cord. 



98. Cerebellar nuclei. — In addition to the superficial cortical 

 gray matter of the cerebellum there are several deep gray masses. 

 The largest of these is the dentate nucleus lying within each 

 cerebellar hemisphere, from whose neurones most of the fibers 

 of the superior cerebellar peduncle arise. Smaller gray masses 

 are found under the vermis near the roof of the fourth ventricle. 

 These are the nuclei emboliformis, globosus, and fastigii. These 

 nuclei are not easily seen in a dissection of a sheep's brain, but 

 may readily be found in either gross or microscopic sections of 

 the human brain. 



See Cunningham ('15), Figs. 511, 512, and 535; Morris ('14), 

 Figs. 637 and 638; Piersol ('13), Figs. 950 and 951; Quain ('09), 

 Vol III, Part 1, Figs. 185-189; Spalteholz ('09), Fig. 743; Toldt 

 ('04), Figs. 1182-1189. 

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