. The Journal of comparative neurology and psychology. of a spindle-shaped cell whose other pole gives rise to thethick dendrite, or from the dendrite itself a short distance from thecell (Fig. 7). In every case in which a true axone was found thethick process entered the descending bundle and the axone pene-trated the substance of the tectum itself. In the rabbit (Fig. 5 D) an occasional bipolar cell is seen whoseslender axone takes an ascending direction. In ordinary stains the cell body is large, pale, uniformly granular. 6o8 Journal of Comparative Neurology and Psychology. and contains a l
. The Journal of comparative neurology and psychology. of a spindle-shaped cell whose other pole gives rise to thethick dendrite, or from the dendrite itself a short distance from thecell (Fig. 7). In every case in which a true axone was found thethick process entered the descending bundle and the axone pene-trated the substance of the tectum itself. In the rabbit (Fig. 5 D) an occasional bipolar cell is seen whoseslender axone takes an ascending direction. In ordinary stains the cell body is large, pale, uniformly granular. 6o8 Journal of Comparative Neurology and Psychology. and contains a large clear nucleus ^yith sharply defined resemblance of these cells in fonn and structural appearance tospinal ganglion cells has been noted or used as a means of descriptionby Meynert and most later authors. This comparison is not only aptas far as general appearance is concerned, but in every particular aclose resemblance can be drawn. The size, the vesicular form, thepossession of small dendrites, the bipolar form with one thick and. B Fig. 8. Two cameia drawings from a transverse section of the brain of ahuman embryo of mm. (Embryo H. 19.) A, the cells and fibers of theradix mesencephalica; B. some cells of the motor nneleus of the magnification is the same in both figures. Only the nuclei are to be seenin most of the cells. one slender process are all duplicated by adult or embryonic spinalganglion cells. The internal structure also is like that of spinalganglion cells, even to the disposition of the neurofibrillse, so far asthese are shown in my silver preparations. In position also thesecells correspond perfectly to the giant cells in the spinal cord offishes and amphibians and to the cells in Amphioxus which arehomologous to the spinal ganglion cells. Johnston, The Radix Mesencephalica Trigeniini. 609 In the liiiman embryo of 15,5 mm. the cells in question are largeand possess large clear nnclei so that they are strikingly differentfrom
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