i8 



ATLAS OF NERVE CELLS 



III. Lateral limiting layer, a layer of white fibres 

 adjacent to the median and posterior gray matter, con- 

 tains short fibres of association, whose origin is from 

 cells in the median portion of gray matter and whose 

 course is similar to those in II. Their termination 

 is about the cells of the same region at different levels. 

 This layer is traversed by many fibres from the other 

 lateral columns, entering and leaving the gray matter. 



IV. Ascending antero-lateral tract, or column of 

 Gowers, lying on the surface of the cord, contains 

 fibres whose origin is in cells situated in the median 

 gray matter. These fibres traverse the other columns 

 and turn upward in this column, passing into the 

 antero-lateral field of the medulla and through the 

 formatio-reticularis of the pons into the internal cap- 

 sule. They transmit sensations of pain and tempera- 

 ture upward to the brain from the cord. Among 

 these fibres in this column are also descending fibres 

 which come downward probably from the cerebellar 

 hemisphere, but do not form a separate column. 



V. Direct cerebellar column, lying on the surface 

 of the cord behind the last named column, contains 

 fibres which arise from the cells of the column of 

 Clarke, and after traversing the other lateral columns, 

 turn upward in this column, and pass to the cortex 



FlG 2 of the cerebellar hemisphere. They transmit sensations 



F.;. 2. - Diagram to illustrate the transmission of sensory, of equilibrium> ( See also Fig. 7 , p. 4 2.) 

 motor, anil association impulses through the spinal cord. 



A, B, C, are three levels of the cord. /, II, ///, are sensory nerve roots entering the posterior root zone at level, B, bifurcating, ascending 

 and descending, and sending collaterals into the gray matter at many levels. Three such collaterals are shown at A, B, C, ending in the posterior 

 horn, and opposite median gray. The collaterals shown in diagrams I and 3 are not shown here. The collateral which crosses to the opposite side 

 terminates about the cell, f, which sends its neuraxon into the column of Gowers, G, and thence upward to the medulla. At level C a collateral 

 ends about sensory cell, A, which sends its neuraxon also into G. The collateral entering the base of the posterior horn terminates about the 

 column of Clarke on the same side. For the sake of distinctness the cell, if, of the column of Clarke is shown on the opposite side with its fibre 

 entering the direct cerebellar column, D, and ascending to the cerebellum, x, descending cerebellar tract sending its collateral fibres into the median 

 gray, e, intrinsic cell of the anterior horn at level, C, sending its neuraxon into the antero-lateral column, z, where it ascends, giving off col- 

 laterals, z, at levels B and A, and proceeding upward to the medulla. ', intrinsic cell at level, A, sending its neuraxon into the antero-lateral 

 column, y, where it ascends and descends, sending its collaterals, y, y, into the anterior horns of levels B, C. P, pyramidal tract giving off collaterals 

 which pass to the anterior horn of the cord and terminate in brushes about the motor cells. The motor cells, in, n, o, are shown for the sake of 

 distinctness on the opposite side, v, anterior median column with collateral entering the anterior horn and terminating in brushes around the 

 motor culls. 



