600 FUNCTIONS OF THE CEREBRO -SPINAL NERVOUS SYSTEM. 



from ^oVu to 20000 f an inch), running transversely, longitudinally, and 

 obliquely. Mingled with these are bloodvessels and some connective tissue. 

 The inner or anterior portion of the Caput also contains longitudinal fibres, 

 to which its opacity is chiefly due; transverse fibres which are continuous 

 with the posterior roots of the nerves and with the longitudinal column of 

 the cord, and cells which are for the most part of small size. 1 Gerlach 2 



FIG. 208. 



FIG. 209. 



FK;. 208. Transverse section of the gray sub- 

 stance of the Human Spinal Cord at the level of the 

 fiiM. Dorsal Nerves ; g, gelatinous substance of 

 Caput Cornu ; h, dark interior of Caput Cornu ; i, 

 Cervix Cornu, containing, j, the posterior vesic- 

 ular column; k, the tractus intennedio-lateralis ; 

 I, Anterior Cornu ; m, Central Canal ; n, Anterior 

 Decussating Commissure. 



Fir;. 209. Median portion of a transverse section of the spinal cord of a child six months old, from 

 the lower part of the cervical region, treated with the double chloride of potassium and gold. Mag- 

 nified 50 diameters, a, a, anterior columns. 6, b, posterior columns, c, central canal, rf, line indicat- 

 ing the epithelium of the central canal, e, connective tissue surrounding the central canal. /, nerve- 

 fibre plexus around the central canal, g, posterior transverse fibres of the gray commissure. A, 

 anterior transverse fibres of the gray commissure, i, decussatiou of fibres in the anterior white 

 commissure. 



observes that the median portion of the gray substance of the spinal cord, 

 the so-called gray commissure, is composed of several distinct histological 

 divisions. Situated slightly in front of the exact centre is the central canal, 

 Fig. 209, c, lined by columnar epithelial cells, Fig. 209, (/, which rest on a 

 membrane composed of connective tissue or ependyma tolerably free from 

 nerve-fibres, Fig. 209, e. Anteriorly to this, and immediately behind the 

 white commissure, Fig. 209, i, are the anterior commissural fibres that (</) 

 immediately bound the sulcus lougitudinalis posterior in the middle line and 

 the posterior columns laterally. The cilia of the columnar cells of the 

 central canal are only present in childhood. A remarkable column of 

 gMiiglionic cells constituting the inner and anterior part of the Cervix Cornu 

 _/', and extending from the lower part of the cord to the middle of the cer- 

 vical enlargement, where it terminates, has been described by Mr. Clarke 

 under the term of the posterior vesicular column. The point of junction of 

 the anterior and posterior cornua () is termed by the same observer the 

 tract us intennedio-lateralis. It extends from the upper roots of the eighth 

 cervical nerves to the lowest part of the dorsal region, but is most prominent 

 about the first and second dorsal nerves. The posterior vesicular columns, 



1 Sec Lurkliart (Murk.-, Phil. Trans., 1858,-p. 240. 



- Art. Spinal Curd, in Strieker's Human and Coinp. Histology, vol. ii, p. 355, 1872. 



