HUMAN AND MAMMALIAN. 41 



CHAPTEUIX. 



THE ANTERO-LATEEAL NUCLEUS. 



The only notice which I find of this important and interesting column is con- 

 tained in a brief description given by Clarke, stating that in the mammalia, " on the 

 outer side of each olivary body, and separated from it by a groove which lodges the 

 hypoglossal nerve, is another vesicular column of nearly the same length, but broader 

 externally. Above, it blends as a flattened band with the trapezium, close to the 

 origin of the facial nerve, which arises from the side of the latter ; and below, it is 

 continuous with a distinct fasciculus of the lateral column. From its side and that 

 of the olivary body, the broad band of arciform fibres crosses the medulla to reach 

 the posterior columns ; but within, it is traversed by a network or plexus, formed 

 by the interlacement of these fibres with those remaining from the anterior cornu, 

 and inclosing the longitudinal bundles of the lateral column. Amongst this net- 

 work lie the cells, which are larger than those of the olivary body, and more 

 irregular in shape. They are oval in difierent degrees, or pyriform, fusiform, cres- 

 centic, club-shaped, triangular, or variously stellate, and give off" processes which 

 nearly encircle the longitudinal bundles, and contribute to form the meshes. All 

 these appearances may be very distinctly observed in the sheep, ox, or cat. In man a 

 similar structure was found, but owing to the difference in the shape of the medulla, 

 it lies behind, instead of at the side of the olivary bodies, and is not so prominent 

 externally; the cells also are rather less than those of the mammalia."^ 



This column of large cells, which, from the variety of its connections, would seem 

 to be of very considerable importance, I have called the antero-lateral nucleus. 

 It is developed in the antero-lateral portion of the medulla, just above the decussa- 

 tion of the pyramids, among the great bundles of arciform fibres which are here so 

 conspicuous. The cells vary, as stated by Clarke, both in form and size, but are 

 mostly quite large, measuring, in the sheep, from -jI-q to -^^-^ of an inch in the 

 principal group ; while behind, a smaller group of very large cells is often foimd, 

 connecting the main nucleus with the caput cornu, some of the cells of which 

 measure -^^-^ to -^\-^ of an inch in diameter. The cells composing the body of the 

 nucleus are disposed in a compact group, through which the arciform fibres radiate 

 in various wavy bundles, forming an intricate network around the longitudinal 

 fasciculi, which are embraced in every direction by the cell-fibres. The large cells, 

 mentioned above, sometimes appear as a distinct group, just on the anterior border 



» Philos. Transactions, 1858, 246. 



