NERVE 111 



The ingoing fibres thus enter the cord, some pass straight 

 up the posterior columns, some enter the grey matter to 

 form synapses with fresh neurons (fig. 49) from which 

 fibres pass up on the lateral and anterior aspects of the cord. 



By tracing these degenerated fibres upwards, it is found 

 that they end as follows : — 



(a) Fibres of the Posterior Columns. — These end in the 

 nuclei of the postero-internal and postero-external columns in 

 the lower part of the medulla oblongata, where they form 

 synapses with fresh neurons. From these nuclei (1) fibres 

 cross to the opposite side and run up in the fillet through 

 the medulla, through the pons Varolii, through the mesial 

 fillet, till they reach (a) the tectum, where they form 

 synapses ; (6) the thalamus opticus, where synapses are 

 also formed ; (2) fibres pass to the cerebellum of the opposite 

 side. 



(b) Fibres in the Lateral and Anterior Columns. — These pass 

 up till the medulla is reached, and here they separate into 

 two distinct sets. 



i. Those going to the Cerebellum. — These are the more 

 marginal set of fibres in the cord. 



(a) Those on the postero-lateral aspect enter the cere- 

 bellum by its inferior peduncle. 



(6) Those on the more anterior aspect enter by the 

 superior peduncle (p. 127). 



ii. Those going to the Tectum and Cerebrum. — These pass up 

 with the mesial fillet, and (a) on reaching the tectum some 

 form synapses there, (h) some run on and end in the 

 thalamus opticus, where they form synapses (fig. 

 50, p. 113). 



(5) Pathological conditions and injuries of the cord in man show 

 that, when the lesion is towards the anterior margin, tactile 

 sensations are abolished, and if it is more in the anterior part 

 of the lateral column painful and thermal sensations are lost. 

 In gunshot injuries to the cord the anterior part is more apt 

 to escape, so that the sensations of touch may persist 

 while painful and thermal sensations are lost. The sense 



