用电镜观察１５～４０周人胎儿脊髓胶状质发育的超微结构变化。结果发现，胎儿胶状质神经元核大、核仁明显，胞浆薄、核搪体少；神经毡内无髓纤维最多，有髓纤维稀少。１５周可见有髓纤维，最宽径自１５至３２周增大明显，以后变化不大；１５至４０周髓鞘最厚处的厚度明显地增厚。２４周出现突触。发育中存在轴－树、轴－轴和树－树突触，以轴－树突触最多见。形成突触的轴突和树突各有两种类型。 The electron microscopic observation of ultrastructural changes in the gelatinous development of human fetal spinal cord at 15-40 weeks. The results showed that fetal gelatinous neurons larger nuclei, nucleoli were obvious, thin cytoplasm, nuclear enamel less; nerve felts no myelinated fibers, myelinated fibers sparse. Myelinated fibers were seen at 15 weeks, with the widest diameter increasing significantly from 15 to 32 weeks, with little change thereafter; thickening of the thickest at 15 to 40 weeks was markedly thicker. Synapse appeared 24 weeks later. Axis-tree, axis-axis, and tree-dendritic synapses exist in development, most commonly seen as axonal-dendritic synapses. There are two types of axons and dendrites that form synapses.