XXX.] SPINAL CORD. 337 



from the grey matter of one side to the white matter of the opposite 

 side. 



(A-.) The posterior cornu. Note the absence of large cells. 

 Only a few small fusiform nerve-cells are seen. Some of the fibres 

 of the posterior root pass into the posterior cornu; some pass 

 directly through the substantia gelatinosa, and others sweep with a 

 curve through the posterior column before they enter the grey 

 matter. The grey matter generally is traversed by fine fibrils, and 

 has a somewhat finely granular appearance. 



(I.) The central canal, lined by a single layer of columnar 

 ciliated epithelial cells. The cilia may be wanting. Near it sec- 

 tions of blood-vessels. In the grey matter observe the plexus of 

 fine fibrils and numerous axis-cylinders. (Multipolar nerve-cells, 

 Lesson XVIII. 9.) 



2. T.S. Human Spinal Cord in several Regions. Stain sec- 

 tions with carmine or lithium-carmine, hsematoxylin, or aniline 

 blue-black, and mount in balsam. Mount sections from the cervical 

 enlargement (fifth nerve) and lumbar enlargement, and compare 

 them with the dorsal section. With the naked eye (and L) 

 observe : 



(a.) The cervical and lumbar sections (figs. 317, 320) are not 

 only larger, but the amount of grey matter is greater than in the 

 dorsal region. Note the large expanded anterior cornu with 

 numerous nerve-cells. In the lumbar region the grey matter is 

 large in amount, the white matter smallest. The white matter is 

 more abundant in the douiftl region and most abundant in the 

 cervical region. This can, to a certain extent, be determined by 

 the amount of white matter lying between the grey matter and 

 the pia mater. There is a gradual transition from the one region 

 of the cord to the other. 



(b.) In the cervical region note a thin septum, which dips into 

 the white matter and divides its posterior column into a smaller 

 internal part the postero-intemal column or column or fasciculus 

 of GoU, and a larger external or lateral part the postero-external 

 column, or fasciculus cuneatns. The grey matter, containing some 

 nerve-cells, also projects into the white matter about midway 

 between the anterior and posterior cornua, forming the inter mcdio- 

 lateral tract. 



(c.) In the dorsal region, observe a group of nerve-cells at the 

 inner part of the neck of the grey matter. It lies behind the plane 

 of the central canal column of Clarke, or posterior vesicular column 



(ii-. 319, cat). 



In sections of the cord at different levels it is important to note 

 the sectional area of the different columns. Thus, Coil's column is 

 largest in the upper cervical region, and diminishes from above 

 30 Y 



