Distribution of Funicular Cells in Different Regions of the Gray Matter
Homolateral funicular cells are, beyond doubt, the most abundant elements of the gray matter, where they form sets which are frequently recognized by their topographic delineation as well as for the special morphologic features of the constituent neurons. This characteristic requires a topographic plan of discussion. It appears at first sight that these neurons should be studied according to a classification based on the axonal termination site. Such a criterion would be excellent if every nucleus of the gray matter contained cells with axons behaving in the same manner. But, just the contrary, many nuclei have cells with very different connections, so that adopting such a classification would imply to forsake completely the topographic pattern.
KeywordsGray Matter Dorsal Horn Substantia Gelatinosa Commissural Axon Dorsal Funiculus
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- 1.It is difficult to decide which is the equivalent of this nucleus among those described by authors in the adult spinal cord; we are inclined, however, to consider it analogous to the lateral nucleus of Bechterew.Google Scholar
- 2.In their figures related to the human column of Clarke, Lenhossék and Van Gehuchten show them without spines. We have not seen them either in the newborn. It is possible also that the spines form at a later date.Google Scholar
- 3.We include in this region the medium cells of Waldeyer, solitary cells, and the dorsobasal nucleus of other authors. We do not separate them because it is impossible to find in the adult and embryonic spinal cord differentiating borders or special morphologic characteristics of their respective neurons.Google Scholar
- 4.In one of our investigations on the substantia gelatinosa, besides the common cellular types with axons going to the dorsal or lateral funiculus, we described other elements with two axons, each entering a different funiculus. But these cells, that were seen in the pigeon embryonic spinal cord, have never been confirmed in later stages of development. We, therefore, consider them now as corresponding to very early phases of cells with bifunicular axons. During the course of development, the initially separate fibers would form a common pedicle, similarly to the occurrence in cells of the spinal ganglia and cerebellar granules. (Cajal, 1891g, 1893b page 41).Google Scholar
- a.Fig. 139.—a, axons.Google Scholar
- b.Fig. 142.—E, central canal.Google Scholar
- c.Cajal uses here the term gray commissure instead of dorsal commissure, which is his general designation for this structure.Google Scholar
- d.This marginal layer is known today as the posteromarginal nucleus or lamina I of Rexed. See annotation a in Chapter X.Google Scholar
- e.The cells of the substantia gelatinosa have been shown to form a closed system, with their axons either remaining within the structure, or returning to it after a relatively short ascending or descending course in the zone of Lissauer or the fasciculus proprius of the lateral funiculus [Szentágothai (1964) J Comp Neurol 122: 219-240].Google Scholar
- f.Fig. 146.—A, B, C, epithelial cells possibly becoming neuroblasts; a, ascending funicular axon; d, descending funicular axon; c, commissural axon.Google Scholar
- g.Fig. 147.—H, fusiform cell with ventral and dorsal dendritic tufts; J, axons entering the dorsal horn bundle.Google Scholar
- h.Fig. 148.—C, terminal arborization.Google Scholar