WHITE AND GRAY SUBSTANCE OF THE CORD. 563 



deeper than the former, which is called the posterior lateral 

 fissure. The bottom of this fissure is formed by the projection 

 of the posterior horn of the cineritious crescent. 

 From the greater depth of this fissure, and from the results 

 of experiments by vivisection upon the spine, it has been con- 

 sidered as subdividing each half of the spinal cord into two 

 columns. The anterior, which comprises all between thig 

 posterior lateral, and the anterior median fissure, is called the 

 motorial column, and that which is behind the posterior lateral, 

 the sensorial column. The anterior forms a large part of each 

 half of the cord, as seen in fig. 221, and is frequently spoken 

 of as the antero-lateral column. At the lower part of the dor- 

 sal, and in the lumbar region, it is one-fourth part larger than 

 the posterior ; in the cervical region it is double the size, and in 

 the medulla oblongata, yet to be spoken of, it forms a still larger 

 portion. 



The white fibres of the cord are very simply arranged, 

 lying parallel to each other ; in consequence of which they 

 are easily stripped off, leaving the surface below smooth and 

 regular, so that, as Sir C. Bell observes, u it appears that the 

 superficial layers, furnish the roots of the higher nerves, and that 

 the lower layers, go off to the roots of the nerves, as they suc- 

 cessively arise." 



The cineritious matter, on making a longitudinal cut of the 

 cord, is seen passing up, as a column of granular matter, and 

 terminating in the medulla oblongata, at the lower part of the 

 fourth ventricle of the brain, and between the corpora restifor- 

 mia, where it forms a grey mass called by Wenzel, tuberculum 

 cinereum. The gray matter of the cord does not, in the adult 

 or in the embryo, present the appearance of separate, gan- 

 glionic masses, of which Gall believed it to consist. It is, 

 however, believed by Miiller, Mayo, Hall, Grainger, Solly, 

 and others, to be entirely analogous in its offices to the nodules 

 of the articulata, though it is not, as in animals of that class, 

 interrupted in the intervals of the attachment of the nerves. 

 This opinion is in accordance with the laws of development 

 in the inferior animals. In the pupa of some insects, the 



