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The effect of floor plate on cellular differentiation in the neural tube of quail embryos was examined. In the developing neural tube the floor plate, which consists of specialized neuroepithelial cells, is located in the ventral midline of the neural tube. When Hensen9s node was extirpated the floor plate and notochord did not develop, and the normal differentiation of the ventral horn motor neurons and dorsal and ventral roots did not occur. When one side of the neural tube was deprived of notochord, the ventro-dorsal differentiation took place on both sides. However, when one side of the neural tube was deprived of the floor plate, the ventral horn motor neurons and dorsal and ventral roots did not develop on that side. These observations suggest that the floor plate influences motor neuron differentiation and acts as an intrinsic organizer to establish pattern and polarity in the developing nervous system.

Early development of the dorsal root ganglia and ventral roots in quail embryos was observed by using HNK-1 antibodies. The dorsal root ganglia showed a dumbbell form in the horizontal plane, i.e. one dorsal root ganglion was constituted by two groups arranged craniocaudally. These observations suggest that the complex form of the dorsal root ganglia is brought about by a subsegmentation of the neural tube and peripheral nerve supply. Further, it was observed that the segmental boundaries of the neural tube, which were indicated by the individual ventral roots, differed from the boundaries indicated by mesodermal segmentation. These findings seem to provide us with a new viewpoint for analyzing the nervous system.

Summary Through stimulation of the lateral amygdaloid nucleus (M of Volsch) we could produce remarkable changes upon respiratory movements, namely, diminution of amplitude and increase in the rate of respiration. The stimulation of the intermediate or medial nucleus of amygdala proper (T or T of Volsch, basal amygdaloid nucleus of Fox) may not bring about changes upon the respiratory movements; if effective, it is typified in the increase in the rate and amplitude of respiration, as it was previously recognized through stimulation of the periamygdaloid cortex. The motion of the diaphragm stands still at the moment of stimulation, regardless as to whether it stands in expiratory or in inspiratory position. The histological observation of the lungs revealed that changes such as hemorrhage, congestion, emphysematous and edematous change, were ext: aordinarily severe in the stimulated side, except in a few instances where much severe damage was shown in the contralateral side.

Summary Through bilateral destruction of the amygdaloid nuclear complex in infant and adult animals and through subsequent observations under careful feeding in sxne period of time, following results were obtained: 1) By bilateral amygdalectomy in infant animals, inhibition in the growth was induced in most cases. 2) Histological observations on the brain lesions of these cases reveal that the inhibitory effect upon the growth may be initiated seemingly by destruction of the medial amygdaloid complex such as nuclei B, D or T, or periamygdaloid cortex such as Pam2 and Pam3, or the anterior amygdaloid region, especially at the level of the nucleus of the lateral olfactory trac:. 3) The inhibitory effect upon the growth was exceedingly obvious in those cases, in which the amygdaloid regions or surrounding structures of these most effective parts of the amygdala were extensively damaged on both sides. 4) Somewhat accelerating effect upon the growth was found in some cases, however, no positive evidence could be gained by any means in this series of observation. 5) Unilateral arnygdalar or hypothalamic destruction cannot result in retardation of the growth, even in those highly convincing cases with tissie deterioration in the vicinity of the amygdala. 6) An example of remarkable obesity was found in an adult cat following bilateral destruction of the medial parts of the amygdala and a part of the entorhinal area. Histological alterations of the internal organs of this case were described and a functional relationship of the so-called feeding centre in the hypothalamus was discussed.

Summary The results of comparative-anatomical and experimental studies on amygdala disclosed the following facts: 1) The division of amygdaloid niiclei into two groups, basolateral and corticomedial seems to be not fully adequate in regard to the functional differences, because results of the stimulation experiments in our laboratory indicate for certain coincidence of effectiveness with autonomous function. From the view angle of fiber connection, this way of division ought also not to be highly evaluated. 2) The intermediate principal nucleus (nucleus T of Volsch large-celled lateral part of the basal nucleus of American authors) is generally divided into two parts, namely, dorsal and ventral portions. The ventral portion of that of the bat is particularly large and together with the large lateral principal nucleus nucleus M of Volsch, lateral nucleus of American authors) constitutes a characteristic of bat amygdala. The reason for its largeness was found, by means of destruction experiment of the amygdaln, in a close connection with the flight activity. Presumably intermediate prinripal nucleus participates in the extrapyramidal motor function; the lateral principal nucleus is generally large in most animals and functionally seems to inhibit motor activity. 3) The medial principal nucleus (nucleus T of Volsch, small-celled medial part of the basal nucleus of American authors) remains maldeveloped in some lower animals. In general, it grows distinctly larger in the caudal level. According to the result of the investigations undertaken in our laboratory, the said nucleus is chiefly related to autonomic nervous system. The above mentioned lateral and intermediate principal nuclei (T and T) also seem to have some relation, partially at least with autonomic nervous system. 4) The so-called medial nucleus in higher animals (D of Volsch) is generally maldeveloped. This nucleus, together with cortical nucleus (B of Volsch), participates partially also in autonomic nerve function. The central nuclei of higher animals (E and E of Volsch) are also underdeveloped 5) The periamygdaloid cortex (Pam1, Pam2 and Pam3 of Rose) receives the fibers from the lateral olfactory tract and evidently participates in olfactory function, but it also causes both extrapyramidal and autonomic reflexes probably by way of the amygdalar connection. Of the said cortical portions what are particularly closely related with amygdala are the portions Pam2 and Pam3. However, the portion Pam3 has not been differentiated yet in the lower animals. 6) When the bilateral amygdala of a young animal is destroyed early in life, growth gets markedly inhibited. In such an animal. atrophy of the parotid gland, thyroid gland, hypophysis, adrenal gland and pancreatic gland was observed. As the cause of this developmental disturbance there are two nervous routes assumable, namely, the route through amygdala hypothalamus anterior lobe of hypophysis general inner secretory glands and the route through amygdala salivary glands inner secretory disturbance of the latter. In the latter connection, the pituitary gland also may participate in the process. We should be particularly cautious about applying bilateral amygdalectomy to human subjects as there is a possibility of the occurrence of disturbances long after the operation. 7) That amygdala participates in salivation was verified by our experiments and the following facts also came to be clear as the result thereof: the portion Pam2 of periamygdaloid cortex has a particularly close connection with the secreting function of parasympathetic origin; of all the amygdaloid nuclei, the medial principal nucleus (T) has an especially close relation with saliva secretion of sympathetic origin, while the intermediate principal nucleus (T), cortical nucleus (B), medial nucleus (D) and hippocampus secret saliva of a parasympathetic origin. Unilateral stimulation produces secretion of bilateral salivary glands. The fibers starting from such portions seem to be led directly toward hypothalamus further to reach the lower part of the brain.