小白鼠个體发生中三叉神经中脑核的初步观察

OBSERVATIONS ON THE DEVELOPMENT OF THE MESENCEPHALIC NUCLEUS OF THE FIFTH NERVE IN THE MOUSE

緒言三叉神經中腦核在英、美敎科書中[1,2]般認爲是單極神經元,它的功能是主持頭部固有覺。但專载中却認爲有多極的細胞[3,4,5],某些文獻[6]和蘇聯的蘇聯書藉[7]有認爲是主管三叉神經供給區内的平滑肌和腺體。要是這樣,則三叉神經中腦核是運動的了。

Serial sections of mouse embryos 11-19 days of vaginal plug age and brain stems of mice of different ages were studied with silver impregnation and Nissl’s methods.The following observations were made:In 12-day embryo,cells of the mesencephalic nucleus were present in the alar plates lateral to the sulci limitans.In 13-day embryo,the caudal end of mesencephalic nucleus reached the level of the motor nucleus of the fifth nerve.In 14-day embryo,a mass of closely packed mesencephalic nucleus cells was also found in the cerebeliar primordium.Most of these cells disappeared later,but some persisted even in adult mice.Cells of mesencephalic nucleus were loosely arranged cranially and densely packed caudally.These cells were most numerous at the level of the motor nucleus of the trigeminaI nerve.In mouse embryos and young mice the cells of the mesencephalic nucleus were more closely packed,and as the brain stems lengthened,they became more and more apart from one another.The number of cells of mesencephalic nucleus increased rapidly in the embryo and reached the maximum at birth.The cell grew more rapidly after birth and reached the size of the adult in about 2 weeks.In the early embryos,nearly all of the cells of mesencephalic nucleus were unipolar.The number of bipolar and multipolar cells increased gradually and became numerous during later stages of intra-uterine life and newborn mice.After birth their number began to decrease gradually,and in 15-day young mice most of the cells became unipolar again.Multipolar cells changed into unipolar ones probably by fusion of their dendrites.Fibers of mesencephalic roots left the brain mainly through the motor root of the fifth nerve,only a portion of them ran in the sensory root.The central connections of the mesencephalic nucleus were traced to the superior and inferior colliculi and to the central gray matter.