18 GRAY SUBSTANCE OF THE MEDULLA OBLONGATA. 



smaller than in the dorsal region; the majority are scarcely larger than those in the 

 middle of the gelatinous substance ; but a few of superior size are unequally scattered 

 amongst them. Above the cervical enlargement the dark masses present nearly the 

 same appearance as in mammalia, but they are rather paler, and the cells they con- 

 tain are of smaller size." (i. c, 450.) 



The existence of the tractus intermedio-lateralis was first pointed out by Clarke 

 in 1851, and described by him subsequently with great accuracy and detail (1859). 

 This tract, which is situated on the lateral border of the gray substance just at the 

 junction of the anterior and posterior cornua, is said by Clarke to gradually disap- 

 pear as it ascends through the cervical enlargement, a few scattered cells remaining, 

 which resemble those of the tractus intermedio-lateralis. 



" In the upper part of the cervical region, a similar but somewhat larger tract 

 reappears in the same situation, and projects in the same way into the lateral 

 column. It increases in ascending to the third pair of nerves. This tract is tra- 

 versed by several roots of the spinal accessory nerve, in their course forwards to the 

 anterior cornu, and contributes with the edge of the posterior cornu to form a 

 beautiful network in the lateral column, through which the nerve enters. There 

 is reason therefore to believe that this tract forms a part of the tractus intermedio- 

 lateralis. In the sheep and ox, and probably in all mammalia, a peculiar group of 

 cells, which is traversed by the roots of the spinal-accessory nerve, is found m the 

 same situation ; and this group in ascending the meduUa oblongata, retires inwards 

 to the space behind the canal, and there contributes, to form the nucleus which 

 gives origin to the highest roots of the nerve. "^ 



The changes which the posterior vesicular columns and the tractus intermedio- 

 lateralis undergo, are very well illustrated in the cat, the two groups being more 

 plainly distinguishable, and their relations more distinctly marked than in any other 

 animal I have examined. At a point near the 2d or 3d cervical nerve, a very dis- 

 tinct, dark, oval mass of cells is seen (CervicaUiern of Stilling),^ situated rather 

 further inward than the posterior vesicular column in the upper part of the cervical 

 enlargement, but so closely resembling it in form and general relation to the sur- 

 rounding fibres, that no doubt can exist of this group being an upward extension 

 of the column. Along the posterior edge of the cervix will be noticed numerous 

 scattered cells. The tractus intermedio-lateralis in this region is very distinct, and 

 is continued outwards along the course of the spinal accessory, forming a projecting 

 mass of gray substance, and is brought into close relation with the longitudinal 

 fascicidi by which the cervix and caput are separated. In the wood-cut. Fig. 2, 

 showing the posterior cornu a little higher up, the group representing the poste- 

 rior vesicrdar column is larger, but rather less distinctly circumscribed (a); it is 

 closely connected with the tractus intermedio-lateralis (/), the cells of which are 

 very numerous, and are continued along the lateral edge of the cervix around the 



* Philos. Transactions, 1859, 451, also 458. 



All these facts have been verified by my own observations, but as they were already so excellently 

 stated by Clarke, I have preferred to give them in his words. 

 " Neue Untersuchungen. Description of pi. iv. 



