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V. — Distribution of the Cells in the Intermedio-Lateral Tract of the Spinal Cord. 

 By Alexander Bruce, M.A., M.D., F.R.C.P.E., F.R.S.E., Physician to the Edin- 

 burgh Royal Infirmary. (With One Plate and Twenty-four Figures.) 



(Read June 5, 1905 ; MS. received November 16, 1905. Issued separately March 6, 1906.) 



The term intermedio-lateral tract was introduced in 1859 [Phil. Trans., 1859, p. 

 445) by Lockhart Clarke to designate a tract or column of nerve cells in the spinal 

 cord, which he had previously described in 1851 [Phil. Trans., 1851, ii. p. 613) as 

 occupying that portion of the lateral margin of the grey matter which is intermediate 

 between the anterior and posterior cornua. According to Clarke's original account, the 

 column in question was very transparent in appearance, and resembled somewhat the 

 substantia gelatinosa of the posterior horn. It was found in the upper part of the 

 lumbar enlargement, extended upwards through the dorsal region, where it distinctly 

 increased in size, to the lower part of the cervical enlargement. Here it disappeared 

 almost entirely. In the upper cervical region it was again seen, and could be traced 

 upwards into the medulla oblongata, where, in the space immediately behind the central 

 canal, it blended with its fellow of the opposite side. In the more complete account of 

 the tract published in 1859 (p. 446), its component cells are described as in part oval, 

 fusiform, pyriform, or triangular, and as being smaller and more uniform in size 

 than those of the anterior cornua. In the mid-dorsal region, where they are least 

 numerous, they are found only near the lateral margin of the grey matter, with the 

 exception of some cells which lie among the white fibres beyond the margin of the 

 grey substance. In the upper dorsal region the tract is larger, and not only projects 

 further outwards into the lateral column of the white fibres, but also tapers inwards 

 across the grey substance, almost to the front of Clarke's column. In the cervical 

 enlargement it gradually disappears, although it seems to contain, in part at least, a few 

 scattered cells resembling those of the intermedio-lateral tract of the dorsal region. In 

 the upper cervical region, as already stated, it is again seen occupying a lateral horn 

 similar to that found in the dorsal region. It is composed of the same kind of cells, 

 and can be followed up into the medulla, where it is said to give origin to some of the 

 fibres of the vagus and the spinal accessory. 



Waldeyer, Gaskell, Sherrington, Mott, and others have drawn attention to the 

 probability that the dorsal vagus nucleus of the medulla belongs to the same system 

 as the intermedio-lateral tract. 



Gaskell has shown that sympathetic fibres pass out with the second and third 

 sacral roots, and Sherrington, without giving a definite opinion on the subject, has 

 suggested that the cells which appear in the sacral region as a lateral horn probably 

 belong to the intermedio-lateral tract system. 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART I. (NO. 5). 14 



