Cajal examined nervous tissue from embryos, and noticed that the axon and dendrites grow out of the cell body of the neuron.
卡哈尔在用胚胎观察神经组织时，发现轴突和树突是从胞体上生出的。
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This led Cajal to formulate the law of dynamic polarization, according to which information flows in one direction through a neuron, from the dendrites, through the cell body, to the axon.