猫の錐体路についての実験的形態学的研究
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概要
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This study has been carried out by the Nauta method to observe the course and termination of projection fibers from the sensory motor cortex to the pons, medulla oblongata and spinal cord in cats with the special reference to the difference between projections from the coronary and sigmoid gyri. The results obtained are summarized as follows. 1. In the reticular formation rows of black dots of irregular shape (rosary-like degenerating axons) are usually only a subject of observations. When rosary-like degenerating axons are scattered in the reticular formation, the distinction of degeneration of terminating fibers from that of fibers en passage is not easy. Only careful observations on the other regions and on the course of degenerating fibers in the reticular formation seem to make this distinction possible with considerable certainty. Degenerating axons in the medial reticular formation at the level between the superior and, inferior olives and at the inferior olivary level, especially at its inferior level, appear to terminate therein. Projections to the reticular formation are bilateral. 2. Projections to the nuclei of Goll and Burdach are nearly completely contralateral. Projection fibers from both sigmoid and coronary gyri to these nuclei are nearly equal in number. 3. Projections to the sensory trigeminal nucleus are also nearly completely contralateral. The coronary gyrus sends more numerous fibers to this nucleus than the sigmoid gyrus. 4. According to Kuypers projections of the sensory motor cortex to the nuclei of dorsal fasciculus and spinal trig'eminal nucleus are sensory feed back. If this view is accepted, the projection to the sensory trigeminal nucleus also can be regarded as the sensory feed back. By our findings the sensory feed back projections appear to show no strict somatotopic localisation, since the relay nuclei of the pathway conducting sensory impulses of the spinal nerves (nuclei of Goll and Burdach) receive projection from the coronary gyrus (face area) and, contrarily, the relay nucleus of the pathway conducting impulses of the trigeminal nerve (sensory trigeminal nucleus) from the sigmoid gyrus (leg area). 5. Projections to the spinal trigeminal nucleus are approximately cohtralateral. The spinal trigeminal nucleus receives fibers from both coronary and sigmoid gyri ; those from the former are much more numerous than those from the latter, and especially at the level between the superior olive and the inferior end of the inferior olive this nucleus receives fibers principally from the coronary gyrus and if any few fibers from the sigmoid gyrus. 6. In the reticular formation situated just medial to the spinal trigeminal nucleus a particular group of degenerating axons can be seen. Some of them are fibers en passage to the spinal trigeminal nucleus, but the pattern of degeneration will show that the certain amount of them terminate in this part of the reticular formation. This projection is nearly contralateral and originates much more numerously from the coronary gyrus than from the sigmoid. 7. The termination of fibers in the motor nuclei of the cranial nerves could not be observed with certainty also in our cases. 8. Degenerating axons following unilateral destruction of the spinal trigeminal nucleus and tract at the level inferior to the middle of the inferior olive can be seen in the medial part of the ipsilateral facial nucleus in two cats. This finding suggests that the region of the spinal trigeminal nucleus is a relay center of the pathway conducting impulses from the coronary gyrus to the facial nucleus. Degenerating axons can not be remarkably found in the hypoglossal, abducens and motor trigeminal nuclei in these two cases. 9. A few degenerating axons are seen in the solitary nucleus. The definite evidence to show the termination of some of them could notabe obtained. Most of them seem to be fibers en passage to the nuclei of the dorsal fasciculus. 10. The ipsilateral projections to the tegmental reticular nucleus of Bechterew are remarkable, while the contralateral one can not be evidently observed. 11. Projection of the sensory motor cortex to the magnocellular part of the lateral reticular nucleus is mainly contralateral and in small number ipsilateral. 12. Degenerating axons can be seen in the dorsomedial part of the inferior olive on both sides, but on the ipsilateral side only in its inferior part. These degenerating axons appear to be mostly en passage. On the contralateral side, however, the possibility that a few of them terminate therein can not be completely denied. 13. The nucleus prepositus n. hypoglossi, nucleus of Roller and f nucleus of Messen and Olszewski receive fibers from the sensory motor cortex. 14. Among the vestibular nuclei the nucleus of Deiters receives bilateral projection. Degenerating axons found in the inferior vestibular nucleus seem to be en passage. 15. In the contralateral dorsal column its central part shows degenerating axons, but in the cervical and lumbar intumescentiae the distribution of degenerating axons extends into the peripheral part of the dorsal column, even into the medial part of the substantia gelatinosa. 16. In the cervical and lumbar segments considerable amounts of degenerating axons can be seen in,the nucleus cornu-commissuralis posterior (Bok) on the contralateral side to lesions. 17. No marked evidence of termination of fibers in the lateral cervical nucleus. 18. Through the whole length of the spinal cord the distribution of degenerating axons are most dense in the lateral part of the contralateral intermediate zone. In the medial part of this zone degenerating axons can be shown in the intumescentiae. 19. In the gray substance of the reticular process degenerating axons are found. Fiber bundles in this region show degeneration at C_2, but not at the other segments. 20. The region of the lateral column on the contralateral side shows a few degenerating axons, but whether or not some of them terminate therein can not be finally determined. 21. Although in our cases the distribution of degenerating axons extends wider into the ventral column than noted in literatures, in accordance with the findings of previous authors if any few degenerating axons can be seen within the groups of motor cells. From the sections stained with the Bubenaite method, however, it is seen that the dendrites of some motor cells extend into the distribution area of degenerating axons. The meaning of this finding and whether or not the pyramidal tract terminates monosynaptically at the dendrites of motor cells will need further study.
- 千葉大学の論文
- 1960-09-28