Hardesty, Medulla Spinalis of the Elephant. 147 



sidered as representing the commissura alba posterior, passing 

 from the dorsal portion of one side of the gray figure to the other 

 side. The ventral portion of the commissura grisea is subdivided 

 by the above longitudinal fasciculi into a number of laminae, or 

 perhaps trabeculae, and is so displaced that the more ventral of 

 these often com^e in contact with the pia mater of the fissura 

 mediana anterior. These ventral laminae seemingly contain 

 little or no neuroglia but are rich in white fibrous connective 

 tissue much of which is probably derived from the pia direct. 

 MeduUated axones are much more abundant in these than in the 

 dorsal lamina and, so far as may be judged from Weigert prep- 

 arations, they are axones arising from cell-bodies situated in the 

 columnae anteriores. They may then be considered as repre- 

 senting the commissura alba anterior (C a. a.. Fig. 8). They 

 may be traced coursing in the laminae, or trabeculae, from each 

 columna anterior and are so numerous that in the mid-line quite 

 an apparent decussation is produced. 



For a more detailed study of the fasciculi coursing longitud- 

 inally in the commissura grisea, attention is first called to their 

 gradual decrease in passing from the cervical through thoracic seg- 

 ments. This decrease may be observed by comparing Figures 9, 

 14, 10, and 13 in the order named. These are details from cervical 

 VI, and thoracic II, IV, and VIII and are reduced to scale 

 from photographs. From an examination of Kopsch's pho- 

 tographs it appears probable that these fasciculi have entirely 

 disappeared in thoracic XVIII. 



To determine the nature of these fasciculi attention is next 

 invited to Figures 2 and 3. These figures show the arrangement 

 of the parts in a transverse section of the medulla oblongata in- 

 volving the decussatio lemniscorum (/?. /. ), the inferior tip of the 

 oliva {O. i.), the radix and nucleus N. hypoglossi (A^. N. h.), and 

 the nuclei of the funiculi posteriores (N. /. g. and N. f. ^.). 

 The pyramids (/*), while not forming so prominent a feature 

 as in the human specimen, for example, are yet sufficiently 

 prominent in the elephant to be easily discerned and in trans- 

 verse section are clearl}/ marked out, even separated by an in- 

 growth of connective tissue. 



