. A manual of diseases of the nervous system. stance,the two being separated by a lateral limiting layer of vertical fibres,in part broken up by processes from the grey matter. In the uppercervical cord, and also to a less extent in the dorsal cord, this layerextends forwards outside the anterior horn, which, in these parts, is * I].£f. by Minkowski, Deut. Arch. f. kl. Med., Bd. xxxiv, p. 433. Slight degene-ration of the pyramidal tracts was the only other lesion. f In the absence of evidence of contrary character, the direction in which fibresconduct must be assumed to be that in which they d
. A manual of diseases of the nervous system. stance,the two being separated by a lateral limiting layer of vertical fibres,in part broken up by processes from the grey matter. In the uppercervical cord, and also to a less extent in the dorsal cord, this layerextends forwards outside the anterior horn, which, in these parts, is * I].£f. by Minkowski, Deut. Arch. f. kl. Med., Bd. xxxiv, p. 433. Slight degene-ration of the pyramidal tracts was the only other lesion. f In the absence of evidence of contrary character, the direction in which fibresconduct must be assumed to be that in which they degenerate. We know of noexceptions to it within the central nervous system. Wherever we can observe therelations this law obtains, except in the peripheral sensory nerves, in which the con-ditions are conspicuously exceptional. Hence the probability is very great that thecorrespondence obtains where we have not yet been able to prove it, and to ignorethe probability because it is not a certainty is scarcely reasonable, although STRUCTURE. 183 narrow. It consists of fine fibres that seem to pass into and out oftlie grey matter. This course, and the fact that the tract does notdegenerate through any considerable extent, suggest that its fibreshave but ashort course, and connect the grey matter of adjacentregions. There is a small tract of fibres, all of small size, at the junction ofthe tip of the posterior horn and lateral column known as Lissauerstract. The fibres come from the posterior roots ; they course upwardfor a short distance, forming the tract, and then enter the posteriorhorn. The rest of the lateral coliimn, in front of the pyramidal and cerebellartracts, consists of fibres that vary insize, course, and date of degeneration, however, asI pointed out some years ago,* enablesus to distinguish an important tractwhich occupies an irregular area infront of the pyramidal and cerebellartracts, and degenerates upwards ^^^^ing degeneration
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