138 Journal of Comparative Neurology, 



cat for example, the difference is very slight. In the more com- 

 monly studied mammals generally, transverse sections taken 

 from the inferior medulla oblongata, the superior cervical seg- 

 ments, from most of the thoracic and from all of the lumbo-sacral 

 segments, are approximately circular in outline. 



The following details may be of interest from the view- 

 point of comparative anatomy. The pia mater spinalis averaged 

 about y^, mm. in thickness. The ligamenta denticulata often 

 attained a width of 10 mm. The fila radicularia of the radices 

 posteriores sometimes attained a width of 6 mm. in the cervi- 

 cal region. Those of the thoracic nerves were of course smaller. 

 In section, the fissura mediana anterior seemed rather narrow 

 in proportion to the size of the specimen, The funiculi pos- 

 teriores are distinctly separated by the septum posterius. The 

 sulcus lateralis anterior is most evident in the pars cervicalis, be- 

 ing indistinct in the pars thoracalis. The sulcus lateralis pos- 

 terior is well marked along the entire length of the specimen. 



Kopsch's observations upon sections were made entirely 

 upon unstained free hand sections of material preserved in 

 Muller's fluid. This accounts perhaps for the fact that he 

 failed to note one of the most unusual and striking peculiarities 

 shown in the medulla spinalis of the elephant. On examining 

 a transverse section, better of the pars cervicalis, and especially 

 if the section has been stained by some method differential for 

 the medullated axones, one's attention is instantly called to the 

 existence of two large and well defined fasciculi coursing longi- 

 tutinally in the commissura grisea. These, occurring one on 

 either side of the mid line, partially split the commissure. They 

 were easily visible to the unaided eye in the formalin preserved 

 material used by the author and in sections stained differentially 

 they become strikingly prominent {F. c. /. , Figs. 7 to 12). 

 The nature of these fasciculi will be more closely examined in 

 the microscopic studies to follow. While Kopsch's illustra- 

 tions (photographs) show these fasciculi, he does not mention 

 them in his observations. That he did not note them is indi- 

 cated in his description of the commissura grisea of which he 

 undoubtedly included them as a part. He states that the com- 



