FUNCTIONAL PARTS OF THE NERVOUS SYSTEM 81 



estimating, but they are very numerous. As elsewhere in anatomical 

 nomenclature, the discoverer's or exploiter's name is attached to some 

 of the columns, but here, fortunately, there are other and preferable 

 names besides. In the anterior portion of the cord, close to the median 

 fissure, is the direct pyramidal tract (Tiirck's), containing those fibers 

 leading from the motor cortex cerebri which do not decussate (cross 

 over) in the medulla. This extends downward only about half-way 

 through the thoracic cord because the axones have been continually 

 giving off collaterals which cross to the anterior horn of the opposite side 

 of the cord. Surrounding this horn of the gray matter is the anterior 

 association-bundle, the so-called antero-lateral ground-bundle. The fibers 

 composing this tract are not long like those of the preceding column, 

 but extend only a short distance each. They are supposed to connect 

 cells of the gray matter. They are the association-fibers, in short, of the 

 cord. Some connect different segments of the cord and so have a vertical 

 course. Others are horizontal in direction and connect the cells of the 

 anterior horn with the anterior nerve-roots (Starr). External to this 

 tract is the narrow antero-lateral column (Lowenthal's) of descending 

 fibers coming in part from the posterior bundle of the medulla and 

 probably from the cerebellum. Vaso-motor impulses may pass down- 

 ward in this column (Starr). Lateral to this and on the periphery of the 

 cord is the antero-lateral column (Gowers 5 ) of ascending fibers, a long 

 tract conveying messages probably from the cord's gray matter to the 

 cerebellum. This column varies much in shape in different parts of the 

 cord; its fibers are more or less confused with those of the descending 

 column; it is called also sometimes the anterior cerebellar tract. In the 

 neck externally between these two last-named columns is the bundle of 

 Helweg, conducting impulses apparently from the olivary body of the 

 medulla. Within the curve of the lateral edge of the gray matter is 

 another association-column, the mixed lateral zone of short fibers. This 

 probably connects minute centers in the gray matter which, although 

 separated spatially, require close functional connection. Outside and 

 posterior to this ill-understood zone is the great crossed pyramidal tract 

 (Tiirck's). This column is smaller and nearer the periphery farther 

 down in the cord because of its gradual loss of fibers into the gray 

 matter of the anterior horns and roots. The two tracts communicate 

 with each other through the cord. It is made up of the 90 per cent, of 

 the efferent motor fibers from the " motor" cortex of the hemisphere 

 which cross over in the medulla. Each tract, therefore, represents the 

 opposite hemisphere. In front of this column is a bundle called 

 Monakow's, which conducts impulses from the red nucleus of the medulla 

 to the gray matter of the cord. 



On the periphery of the cord and external to the column just considered 

 is the direct cerebellar tract (Flechsig's). The impulses which pass up 

 this column (muscle and joint " sensations" in part) arise more or less 

 directly from the gray matter on the outer side of the posterior horn 

 (Clark's column) and pass to the upper worm of both sides of the cere- 

 bellum by way of the restiform body. This is the vegetative tract of 

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