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THE NERVE SYSTEM 



nuclei arise axones which pass (1) to the thalamus and cerebral cortex (links in 

 the cerebello-cortical neurone-chain), and (2) axones which descend into the 

 spinal cord to form the tractus rubrospinalis (Monakow's) a continuation of an 

 indirect motor path from the cerebral cortex to the peripheral motor nerve. The 

 tracts arising from the red nuclei of the two sides decussate with each other and 

 descend in the tegmentum. 



POSTERIOR 

 COMMISSURE 



SPECIAL NUCLEUS 

 OF THE MEDIAL 

 LONGITUDINAL 

 BUNDLE 



FOUNTAIN 

 DECUSSATION 



NFERIOR 

 OUADRIGEMINA 



LATERAL 



LEMNISCUS 



SUPERIOR 

 QUADRIGEMINA 



FIG. 662. The medial longitudinal bundle. (The nuclei may be identified by comparison with Fig. 646.) 



In the intercrural space lies a primitive gray ganglionic mass, the posterior 

 perforated substance or postperforatum. In this posterior perforated substance, 

 cephalad of the pons and in the median line, lies a cluster of cells, the interpeduncu- 

 lar nucleus (Gudden). The fasciculus retroflexus (Meynert), whose fibres arise 

 in the habenal ganglion, descends to end in the interpeduncular ganglion. 



The principal longitudinal fibre tracts in the tegmentum of the mid-brain are (1) 

 the medial longitudinal fasciculus, (2) the lateral lemniscus, (3) the medial lemniscus, 



