Histological Studies on the Course and the Endings of Hypothalamo-hypophysial (Neurosecretory) and Tuberohypophysial Tracts

Abstract

In the hypothalamo-hypophysial system of the dog, the cat, the rabbit and the calf, observation was made on the running of the hypothalamo-hypophsial neurosecretory tract and tubero-hypophysial tract, and especially on their endings. The methods used were BIELSCHOWSKY-GROS' impregnation, its modification by the author, and the latter method combined with GOMORI-HALMI's aldehyde-fuchsin staining (41st report). The results obtained are as follows:1. Some of the neurosecretory fibers terminate freely, without forming any network, in the bordering area between‘Zwischenstück’and the lobus tuberalis, and also in the wall of the infundibular recess of the third ventricle. Some of the endings in the bordering area between‘Zwischenstück’and the lobus tuberalis take the shape of an end-bulb 15μ long and 10μ wide, and sometimes their swellings are filled with argyrophil granules showing granular disintegration. The endings in the venticular wall are observed between ependymal cells or sometimes slightly protruded into the ventricle.2. There are nodular or non-nodular delicate nerve fibers in the external layer of the infundibulum and in GREVING's infundibular islets, and in the posterior lobe. These nerve fibers, fine and AF-phobe, and probably not belonging to the neurosecretory tract, seem to have an intimate relation with the blood vessel.3. In the dog some nodular nerve fibers are noted not only in the hypophysis but also in the tuber cinereum, but none in the neurosecretory nucleus and in the mamillary body. A few nodular nerve fibers are noted also in the neurohypophysis of the cat, but they are less in comparison with those of the dog. The nodular or non-nodular, AF-phobe nerve fibers are presumably nerve fibers belonging to the tubero-hypophysial tract, and it seems that the nodular ones are those which have differentiated especially remarkably in the dog. In animals other than dog and cat, no nodular nerve fiber could be found.4. Nodular and non-nodular AF-phobe nerve fibers run along with the blood vessel, or quite independently from it, to enter the lobus tuberalis and the‘Umschlagszone’. But the number of such nerve fibers is small and it is impossible to follow their courses long after their entrance. There are no findings obtained of the fibers terminating in gland cells.5. In the anterior lobe too, a few nerve fibers but comparatively many in the rabbit-are noted to run together with or independently from the blood vessel, but their origin is unknown.6. Only in the rabbit, it is observed that neurosecretory nerve fibers run out of the posterior lobe and enter the lobus intermedius.7. No nerve cells were perceived in the adenohypophysis of animals used.8. The partial crossing of the hypothalamo-hypophysial tracts of both sides are noted in the hilus area of the posterior lobe.9. Some of the nerve fibers of the hypothalamo-hypophysial tracts terminate at the pituicytes in the posterior lobe.10. In the posterior lobe too, there are sometimes observed end-bulb shaped nerve endings, which often show an argyrophil-granular disintegration in its interior. This type of nerve ending generally exists some distance away from the blood vessel.