The educational meaning of manual arts and industries . Fig. 4.—Isolated body of a large cell from the ventral horn ofthe spinal cord. Human, X 200 diameters. (Obersteiner.)A, neuron; D, dendrons; N, nucleus with* enclosures; P,pigment spot. In the central system these prolongations extend from the cortex of the cerebrum to the lumbar en PHYSICAL AND PHYSIOLOGICAL RESULTS 121 largements of the cord, and in the peripheral systemthey reach from their point of origin in the cord tothe most distant portions of the extremities. In eachinstance the fiber is a continuous growth of the cellbody. Thus
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The educational meaning of manual arts and industries . Fig. 4.—Isolated body of a large cell from the ventral horn ofthe spinal cord. Human, X 200 diameters. (Obersteiner.)A, neuron; D, dendrons; N, nucleus with* enclosures; P, pigment spot. In the central system these prolongations extend from the cortex of the cerebrum to the lumbar en PHYSICAL AND PHYSIOLOGICAL RESULTS 121 largements of the cord, and in the peripheral systemthey reach from their point of origin in the cord tothe most distant portions of the extremities. In eachinstance the fiber is a continuous growth of the cellbody. Thus the outgrowths may become quantitativelythe more important portion of the cell, sometimes equal. Fig. 5.—A-D, showing the phylogenetic development of maturenerve cells in a series of vertebrates; a-e, the ontogeneticdevolepment of growing cells in a typical mammal. In bothcases only pyramidal cells from the cerebrum are shown. A, frog; B, lizard; C, rat; D, man; a, neuroblast without den-drons; b, commencing dendrons; c, dendrons further de-veloped; d, first appearance of collateral branches; e, furtherdevelopment of collaterals and dendrons. From S. Ramony Cajal.) 122 MANUAL ARTS AND INDUSTRIES in volume to 500 times the cell body, and sometimesare even less than the cell body. Further, it seems thatgenerally small cell bodies have neurons of small dia-meter and large cell bodies have neurons of large dia-meter. It is believed that the generation of new nervecells ceases with the third month of foetal life, butafter this time the total volume of the whole nervoussystem increases about 47 times. Since it is knownthat some parts of the system increases 10, 000 timesthe original vo