152 Journal of Agricultural Research voi. xvin. No. 3 



these tracts in domestic animals is quite limited. We must recognize, 

 however, in the white matter three classes of nerve fibers : those entering 

 the cord from the periphery of the body, those entering from the brain, 

 and those arising from the nerve cells situated within the cord itself. 

 Fibers constituting the pathways for the transmission of impulses from 

 lower to higher levels form the ascending tracts, while those fibers in 

 which the impulse is conducted in the opposite direction form the descend- 

 ing tracts. The medullated fibers in the column of Burdach and the 

 column of Goll were more affected than the fibers in other columns. 

 The fibers of the dorsal column consist of two sets of axones. The afferent 

 or sensory axones, which come from the cells of the spinal ganglia, enter 

 as the dorsal roots of the spinal nerves and divide into two branches. 

 The anterior ascending branches from the sensory pathway to the brain, 

 extend to the fasciculus cunlatus and fasciculus gracilis, or corresponding 

 tracts, to the nuclei in the medulla oblongata. The posterior descending 

 branches extend backward for varying distances and give off numerous 

 collaterals to the cells of the gray column, thus forming part of the 

 mechanism for the mediation of reflex action. Some collaterals cross in 

 the white commissure to the opposite side. The second set of axones 

 arise from the smaller cells of the gray column. They enter the white 

 matter and divide into anterior and posterior branches, forming the 

 fasciculi proprii or ground bundles of the cord. The function of this set 

 of axones is chiefly to associate various levels of the cord. 



SPINAL GANGLIA 



In removing the spinal cord, the spinal ganglia of the cervical and 

 dorsal regions became detached. The ganglia of the lumbar enlargement 

 and the sacral region alone were saved so that only a limited number of 

 these ganglia could be examined. The same stains were used as for the 

 staining of the brain and spinal cord. All ganglia appeared to be en- 

 larged. The capsules were thickened. Many of the peripherally disposed 

 nerve cells appeared normal in size. The nuclei and the chromatophil 

 granules were well stained in some and much paler in others where the 

 chromatophil granules were not only reduced in size but almost disinte- 

 grated and scattered among these average-sized cells. Smaller, irregu- 

 lar, shrunken cells were present, in which the disintegration was more 

 marked. These latter cells took the staining very poorly and had the 

 nucleus displaced toward the periphery. But even in these cells the 

 nuclei had not entirely lost the staining property. The partial dis- 

 integration of the chromatophil granules and the pale color of the 

 shrunken or sclerotic cells indicated varying degrees of chromatolysis. 

 The interstitial tissues in the interior of the ganglia were increased in 

 amount and showed in places clusters or groups of round-cell accumula- 

 tions. In the sacral ganglia a greater number of shrunken cells were 



