[Qualitative and quantitative study on ontogenesis of nucleus nervi hypoglossi in male Tupaia belangeri].

The change of the number of neurons, of the freshvolume, of the density of neurons, of the relative volume (freshvolume of hypoglossal nucleus/freshvolume of the whole brain) and of the length of the hypoglossal nucleus of 30 male Tupaia belangeri aged 36 to 388 days of ontogenesis has been studied using the logistic function (see article) for increasing values and the exponential function (see article) for decreasing values. The number of neurons is decreasing at 36 days of ontogenesis from 5700 to 5150 on the adult level, the density of neurons from 30000 N/mm3 to 6000 N/mm3 and the relative volume from 0,8% to 0,26%. The freshvolume is increasing from 0,31 mm3 on birth to 0,92 mm3 on the adult level and the length from 1,74 mm to 2,41 mm. The development of hypoglossal nucleus of Tupaia belangeri during ontogenesis starts very early in comparison with the whole brain. The half-value time of the growth of freshvolume is 53 days of ontogenesis and that of the growth of length is 34 days of ontogenesis. The maximum of spontaneous cell loss, stated here too for the hypoglossal nucleus, probably lies before the 36th day of ontogenesis. The decrease of the relative volume during ontogenesis is a further characteristic fact of the very early start of the development of hypoglossal nucleus of Tupaia belangeri during ontogenesis.