ANATOMY AND PHYSIOLOGY OF THE BRAIN. 411 



larger, especially in a sense transversely from side to side, 

 and more flattened from above downward. The increase 

 of bulk depends on the presence of a considerable amount 

 of grey matter in its substance, on new fibres originating 

 from this and passing in a longitudinal direction, and on 

 numerous transverse fibres passing across between the vari- 

 ous grey nuclei or coming from parts adjacent to the me- 

 dulla. The superior and inferior fissures, which are so 

 noticeable in the spinal cord, have almost disappeared in 

 the medulla. 



On the lower aspect of the medulla, we observe on 

 each side of the median line a pyramidal mass (anterior 

 pyramid) of white matter, wider and more diverging from 

 its fellow in front than behind. It is not continued back 

 into the cord, but makes its appearance on the lower aspect 

 of the medulla, where many of its fibres seem to arise from 

 masses of grey matter, and terminates anteriorly in the pons 

 Yarolii. Its internal fibres, which, according to Stilling, 

 represent the motor-fibres of the lateral column, decussate 

 in the median line with similar fibres from the opposite 

 side ; and it is here, accordingly, that volitional motor force 

 crosses from one side to the other. The rest of its fibres 

 pass up to the brain on the same side. It consists entirely 

 of white nervous matter. The restiform bodies are two rope- 

 like bodies on the outer side of the anterior pyramids. 

 They are continuous with the posterior, and part of the 

 antero-lateral, columns of the cord, but are made up also in 

 great part of fibres originating from grey masses in the 

 medulla, and of others descending from the cerebellum, 

 into which it seems to be continuous, forming its posterior 

 peduncle. On the superior aspect are seen two pyramidal 

 bodies (posterior pyramids), which originate in some fibrous 

 bundles on each side of the superior median fissure, and on 



