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A MANUAL OF PHYSIOLOGY 



most ; beneath these come fibres from the lowest thoracic seg- 

 ments, then fibres from the higher thoracic segments ; and, 

 internal to all, fibres from the topmost thoracic and lowest 

 cervical segments (Sherrington and Laslett). 



Connections of the Antero-lateral Ascending Tract. According 

 to Schafer, the axons of this tract are probably connected with cells 

 situated in the middle and posterior parts of the grey crescent, 

 mainly on the opposite side of the cord, although also on the same 

 side. None of the fibres of the tract can come directly from the 

 posterior nerve-roots, since no degeneration is seen in it on section 

 of the roots alone. 



The antero-lateral ascending tract passes up through the medulla, 

 where some of its fibres perhaps form synapses with the cells of the 

 lateral nucleus, a collection of grey matter in the lateral portion of 

 the spinal bulb. But its main strand runs on unbroken through the 

 medulla, in front of the restif orm body, and behind the olive, and after 

 reaching the upper part of the pons bends back over and in company 



with the superior peduncle as 

 the ventral spino - cerebellar 

 bundle, to end in the worm 

 of the cerebellum (Fig. 330). 



A few fibres of Gowers' tract 

 may pass by the middle pe- 

 duncle to the opposite cere- 

 bellar hemisphere. Some of 

 its fibres do not go to the 

 cerebellum at all. One group 

 can be followed to the cor- 

 pora quadrigemina (spino- 

 tectal fibres), and another by 

 way of the tegmentum of the 

 crus cerebri to the optic thala- 

 mus (spino-thalamic fibres] . 



FIG. 323. -DIAGRAM OF DECUSSATION Through the relay of the 



OF FILLET. gracile and cuneate nuclei, 



a, nucleus gracilis ; b, nucleus cuneatus ; the pOStero-internal and pOS- 



c, internal arcuate fibres crossing the 

 middle line from a and b to the fillet d, 

 and forming the decussation of the fillet ; 

 c, anterior median fissure. 



tero-external columns of the 

 cord are further connected 

 on the one hand with the 

 cerebrum, and on the other 

 with the cerebellum. The cells of the nuclei give off fibres 

 (internal arcuate fibres) which, sweeping in wide arches across 

 the mesial raphe to the opposite side, take up a position 

 behind the pyramid in the tract of the fillet, a bundle of fibres 

 which becomes more compact, and therefore more distinct as it 

 passes brainwards. Receiving fibres from other sources on its 

 way, and also giving off fibres, it runs upwards through the 

 dorsal or tegmental portion of the pons. In the mid-brain it 

 divides into two portions, the lateral fillet, also called the lower 

 fillet or fillet of Reil, and the intermediate, also called the upper 



