关键词: 发育, 运动神经元, 脊髓, 山羊

Abstract: The development of motor neurons in the ventral horn of spinal cord in prenatal goat were observed by light microscope and electron microscope. The results showed: (1)The form of motor neurons in the ventral horn of spinal cord underwent four developing phases: the undifferentiation neurons, the immature neurons, the youthful neurons and the ripe neurons; (2)With the development of the motor neurons the nucleus were enlarging，the heterochromatin was reducing and tending to distribute in the peripheral gradually. With the number of nucleolus decreasing, the central nucleolus occurred in eighth week, and it become to develop after that the karyotheca matured gradually; (3)The changes in the development of endomembrane system of the motor neurons accorded with that of motor neurons.

Key words: development, motor neuron, spinal cord, prenatal goat