ヒトの顔面神経の線維分析的研究

Abstract

After an Orth's solution was infused into a 45 years-old male, who had no nervous disorder, the facial nerve was removed in each portion from proximal to peripheral. These materials, after fixed again with an Orth's solution and then with a Muller solution, were made into refrigerated cross sections, which were given the myelin sheath staining with Kultschitzky's hematoxylin and enclosed in the glycerin including 5% gelatin. Then the diameter of the medullated nerve fibers and their axis-cylinders in each preparation were measured under an oil immersed lens of 1, 000 magnifications by an ocular micrometer. From the fiber diameter distribution histograms gained from the measurement and the per cent ratios (g) of the axis-cylinders to the fiber diameters, the fiber analysis was made, obtaining the following results. 1. The medullated fiber diameters in the facial nerve trunk (that is, proximal and distal portions of the geniculate ganglion, and proximal one just after branching the chorda tympani) extended from 0.5 to 16μ, whose distribution consisted of the small fiber group with the peak between 3 and 5μ and the large fiber group with the peak between 8 and 10μ. It was speculated that the small fiber group consisted of parasympathic nerve fibers and taste ones, and the large fiber group the motor nerve fibers. 2. The diameters of medullated fibers constituting the greater petrosal nerve ranged from 0.5 to 12μ, and showed a distribution with one peak between 3 and 5μ declining slowly to a large fiber. It was speculated that this nerve mostly consisted of parasympathic nerve fibers and partly of taste ones. 3. The diameters of the medullated fibers constituting the chorda tympani ranged from 0.5 to 13μ, and showed a distribution with one peak between 3 and 5μ declining slowly to a large fiber. It was supposed that this nerve consisted of two kinds of nerve fibers, parasympathic nerve fibers and taste ones. 4. The diameters of medullated fibers constituting the facial nerve just below the stylomastoideal foramen ranged from 1 to 15μ, and showed a regular distribution with one peak between 8 and 9μ. It was supposed that this nerve consisted of pure motor nerve fibers. 5. The diameters of medullated fibers constituting the temporal, the buccal, the mandibular marginal and the cervical branches ranged from 1 to 15μ ; they consisted of a great quantity of large fiber group with a peak between 7 and 9μ and only a little of small fiber group with a peak between 3 and 5μ. Though it was speculated that a large fiber group consisted of the motor nerve fibers, it is very difficult to decide whether the small fiber group originated in the distal excesses of the motor nerve fibers or the inter-mixes of the sensible nerve fibers. 6. The per cent ratios (g) of the diameters of the axis-cylinders to those of the fibers tended to increase acutely in the small fiber group, while slowly in the large fiber one along with the increase of the fiber diameter, so that g value should be considered to indicate the functional difference between the small and large fiber groups.