506 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



spinal cord constitutes the basis of the posterior cornu. Still 

 higher up, this vagal nucleus becoming confined to the anterior 

 angle of the grey floor (fig. 257), whilst the auditory nucleus 

 and eminentia teres diminish in size, passes forward as the 

 ala cinerea to the plane of the grey floor, and entering the 

 accessory nucleus is situated to the side of, and behind, the 

 central canal (fig. 258, XI 1 ). The vago-accessory nucleus con- 

 tains a number of scattered darkly pigmented nerve corpuscles 

 of nearly equal size, and has on its outer side a cluster of fusi- 

 form cells having a length of 21 24 ju, and a thickness of 6 ju, 

 bounded by a peculiar convolute of very fine fibrils, the former 

 becoming visible with the disappearance of the auditory 

 nucleus, and after the closing in of the central canal appearing 

 connected with the commissure enclosed in the bolt (Obex). 

 These fusiform cells extend towards the origin of the root. 



Opposite to the vago-accessory nucleus, and enclosed by the 

 transverse sections of the posterior division of the medulla 

 oblongata, is situated the anterior column of origin of the 

 lateral mixed system (fig. 257 x 2 ), in the form of an oblong 

 nucleus lying at a distance of three millimeters from the 

 grey substance of the central cavities, composed of multi- 

 caudate nerve corpuscles 60 /m long and 21 JJL broad, between 

 which the fibrse arcuatse of the origin of the posterior column 

 pass through, and are distinctly continuous with their long 

 processes. Deiters, in accordance with his views of the motor 

 fasciculi of the origin of the vagus, has correctly understood 

 the significance of this nucleus, whilst Clarke, in consequence 

 of his misapprehension of the inferior facial nucleus, regards 

 it as a continuation of the motor nucleus of the fifth. 



It is important to distinguish it from the more posteriorly 

 and externally situated nuclei of the lateral column, which was 

 included under the cluster formations. 



This anterior nucleus of origin of the lateral system repre- 

 sents in the medulla oblongata the processus lateralis of the 

 anterior cornu of the spinal cord. The former allows the 

 upper, the latter the lowermost, fasciculi of origin of the lateral 

 system to arise from it as the accessory nerve (fig. 261, xi). 



An elongated, tolerably close cluster of large fusiform radially 



