148 Journal of Comparative Neurology. 



Figures 4 and 5 represent a section passing through the 

 beginning nucleus fasciculi gracilis {N. f. g.) and through the 

 decussatio pyramidum (Z?. p.). Figure 6 is a detail showing 

 the ventral portion of Figure 4. The pyramids (P ) are not so 

 prominent as in Figure 2 since many of the axones composing 

 them have passed dorsalward in the process of decussation. 

 The fissura mediana anterior is partially obliterated by the 

 decussation and the pia mater sends connective tissue 

 trabeculae into the midst of the decussation. Attention is 

 especially called to the fact that there is no indication of the 

 decussating pyramidal axones passing over to the funiculi later- 

 ales of the opposite side. The columna anterior (ventral horn) 

 is intact and, with the exception of having less depth, its form 

 here is very similar to its form in cervical I and II, or well be- 

 low the decussatio pyramidum. In those specimens, human 

 especially, in which the decussating axones are known to pass 

 over into the funiculi laterales of the opposite side, one of the 

 most striking features of a section at this level is the almost 

 entire obliteration of the columna anterior. In order to attain 

 their lateral position in the fasciculus cerebro-spinalis lateralis 

 (crossed pyramidal tract), the axones pass through the columna 

 anterior in such abundance and so disperse its substance that 

 only its most ventral margin remains intact. The sections show 

 that this is not the case in the elephant. Under the microscope 

 the pyramidal axones are seen to decussate abundantly, but 

 instead of passing through the columna anterior to assume a 

 more lateral position, they remain mesial to the columna ante- 

 rior and at first go to form fasciculi in the more dorsal portions 

 of the funiculi anteriores. Very few, if any, seem to pene- 

 trate the substantia grisca at all. Numerous trabeculae from 

 the columnae anteriores pass into and through the intervening 

 fasciculi and these trabeculae contain medullated axones. Some 

 of these axonesare, perhaps, contributed from the fasciculi in ques- 

 tion, but of these it can not be said that an appreciable number 

 pass through the columna anterior to the lateral funiculi. As 

 pyramidal axones, many would terminate within the substantia 

 grisea. Many of the axones found in the trabeculae, arise, no 



