. A treatise on mental diseases. on send out from thepointed end a projecting stem, which afterward becomes the axiscylinder of the nerve cell. Even on the fourth day of embryoniclife in the chick the axis cylinders have attained a perceptiblelength, and have on their distal extremity an irregular conicalswelling, the growing end or cone de oroissance of Cajal. Up tothis stage the body of the cell has remained smooth, but during thecourse of the fifth day (Lenhossek) branches start from the sides 18 A TREATISE ON MENTAL DISEASES in the form of varicose projections, to be the future processes o
. A treatise on mental diseases. on send out from thepointed end a projecting stem, which afterward becomes the axiscylinder of the nerve cell. Even on the fourth day of embryoniclife in the chick the axis cylinders have attained a perceptiblelength, and have on their distal extremity an irregular conicalswelling, the growing end or cone de oroissance of Cajal. Up tothis stage the body of the cell has remained smooth, but during thecourse of the fifth day (Lenhossek) branches start from the sides 18 A TREATISE ON MENTAL DISEASES in the form of varicose projections, to be the future processes ordendrites of the cell. These branches become more and morenumerous, less varicose and irregular, and though retaining to amuch later period some of the aspects of embryonal life, soonassume all the attributes of the perfect nerve cell. Seen in the pyramidal nerve cell, numerically by far the mostabundant nerve element of the cortex, and one giving to it its dis-tinctive character, the development of the neuroblast is peculiarly. Fig. 4.—Growth of the Neuroblast. 1, Neuroblast of pear-shape with the beginningof the axonal extension; 2, the primordial dendrite is beginning to sprout and showbranches; 3, a somewhat later stage; the axone shows budding collaterals; 4, a basaldendrite shows at the lower margin of the body; the primordial dendrite has grownconsiderably; 5, numerous branches have made their appearance at the sides and baseof the body, the primordial process has extended, and the collaterals have branches;6, full-grown nerve cell of the pyramidal type. Modified from Cajal. characteristic and beautiful. Like all its congeners, the primitivecell is of pear form, with the axis cylinder proceeding from thethinnest and lowermost portion of the protoplasmic body towardthe central regions of the hemispheres (Fig. 4). Soon at the oppo-site pole appears an outgrowth of protoplasm, surmounted by a tuft HISTOLOGY OF THE CORTEX 19 of short branches. This outgrowth lengthens rap
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