The histological characteristics of the adrenocortical tissue of twenty-two species of birds belonging to seventeen orders are described in this report. This histological survey serves to show that there are structural peculiarities associated with different species, and wide variations with regard to cytomorphism, nuclear polarity and other cytological features can be distinguished. On the basis of histomorphic organisation the avian interrenal can be classiffied into six structural categories illustrating specialisation into two zones, and a differentiation from a relatively simple to more complex types. Thus, birds like the chick, swift, crow and the snipe (type I) show no zonal specificity in their interrenal tissue. Histomorphic zonation in the periphery and the centre is first recognizable in the adrenals of the myna, sparrow, pigeon, kite and the nightjar (type II). A moderately differentiated zonal pattern is found in the kingfisher, egret, cuckoo, duck, owl, stint, cormorant, waterhen and the woodpecker (types III and IV). Types V and VI include the dove, quail, flamingo and parakeet, and represent an extreme cytological zonation in their interrenals. This investigation raises the possibility that the interrenal organ in many birds possesses a zonal specificity. No phylogenetic trends are apparent from the study of these interrenal patterns.

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Fine structures of the locus coeruleus of the rabbit, in particular the synaptic organization, were studied with the electron microscope.
Synaptic contacts occurred much more frequently on the dendritic profiles than on the neuronal somata. No axo-axonal synapses were encountered. Many synaptic bags contained a large number of closely packed round agranular vesicles; synaptic bags filled only or chiefly with flattened vesicles were less common. The synaptic densities usually were symmetrical in the synaptic terminals with flattened vesicles. A few dense-cored vesicles of 500-1, 000Å diameter were often found within these synaptic bags; these vesicles, however, were almost always more or less apart from the presynaptic membrane. On rare occasions, a few dense-cored vesicles were also found in the neuronal somata. The nucleolus-like bodies in the subsynaptic areas, the synaptic vesicles aggregated in a crystal-like array, and the subjunctional bodies were also observed.
On the third or fourth day after making electrolytic lesions in the hypothalamus, the mesencephalic central gray or the mesencephalic dorsal tegmentum, electron-dense degenerated synaptic bags were found in the locus coeruleus ipsilateral to the lesions. The degenerated synaptic bags usually contained round vesicles and were in contact with large or medium-sized dendritic profiles. A few degenerated synaptic bags containing somewhat elongated vesicles were also encountered in the locus coeruleus of the rabbits with lesions involving the mesencephalic central gray and the mesencephalic dorsal tegmentum. No degenerative changes could be found in the axosomatic synaptic terminals.
Possible functional meanings of the hypothalamic and mesencephalic projections to the locus coeruleus were discussed.

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Tissue samples were fixed by several methods, stained with lead citrate and uranyl acetate, and evaluated with the electron microscope. The secretory cell cytoplasm of lateral nasal gland contained an extensive Golgi apparatus, well developed rough endoplasmic reticulum, and numerous mitochondria. The granules were associated with rough endoplasmic reticulum, Golgi zone, mitochondria, or with other granules with which they coalesced. The junctions between the acinar cells were zonulae occludentes, zonulae adhaerentes, and maculae adhaerentes in that order from the lumen to the cellular base. The macular complexes included, in addition to transverse fibers, intracellular filaments that extended parallel to the cellular wall. These latter fibers were observed in the cellular interior, after they had separated from the peripheral zone. Numerous preterminal nerve fibers were present in the interacinar spaces. They passed from there through the basement membrane to come in contact first with the base of the cell, and then with the intercellular space. The nerve terminals within an acinus, surrounded by a unit membrane, contained mitochondria and small agranular vesicles. In spite of a close relationship between a nerve terminal and the secretory cell, a synaptic ending was not identified in the lateral nasal gland.

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Using a combined cytophotometric-autoradiographic technique, the authors have detected in the snake Xenodon merremii an acid polysaccharidic complex in the serous acinar cells of upper labial salivary gland, the mucous cells of the excretory duct of Duvernoy's gland, the goblet cells of large intestine and intercellular matrix of tracheal cartilage. In a previous study, this same technique failed to demonstrate in this species the presence of mast cells, known to contain sulfated acid polysaccharides, suggesting that these cells do not occur in this animal species.

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The early reactions in the spleen and mesenteric lymph node following a single injection of typhoid-paratyphoid vaccine in the mouse were histologically examined.
The splenic lymphoid tissue, white pulp, is topographically divided into five portions; periarterial area, follicular area, germinal center, outer cap region of germinal center and marginal zone. The marginal zone and periarterial area are the integral portion selectively involved in the early immune response. In the marginal zone, a remarkable depletion of small lymphocytes and a diffuse accumulation of polymorphonuclear leucocytes occur immediately after vaccine injection. The loss of small lymphocytes persists for a short period, but the infiltration of polymorphonuclears soon becomes less marked. Simultaneously with the changes in the marginal zone, prominent changes are observed in the periarterial area. The periarterial area initially is transiently packed with small lymphocytes, but subsequently becomes depleted of small lymphocytes. At 24hrs after vaccine injection, however, both the marginal zone and periarterial area are repopulated with small lymphocytes as tightly as before antigenic stimulation.
The mesenteric lymph node is topographically divided into three areas; cortical, paracortical and medullary areas. In response to antigenic stimulation, a depletion of small lymphocytes from the paracortical area occurs initially, but the area is soon repopulated with small lymphocytes.
These early events occurring in the specific topographic regions of the lymphoid organ after antigen injection appear to represent morphologic alterations during the “induction” or “latent” phase in the immune response. The nature and significance of the specific regions selectively involved in the early immune response were discussed particularly in relation to the dynamic functional structure of the peripheral lymphoid organ.

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HeLa S3 cells and primary cultured cells of mouse kidney have been studied using scanning electron microscopy and differential interference microscopy. After photomicrographs were taken with the differential interference microscope, the cells were fixed with either 1% osmium tetroxide or 2.5% glutaraldehyde, and then the same fields as the differential interference photomicrographs were photographed again in the scanning electron microscope. The results of differential interference microscopy revealed that most of the nuclei of HeLa cells and mouse kidney cells appeared thinner than the surrouding cytoplasm. On the other hand, the observations of scanning electron microscopy revealed that nuclei thinner than the surrounding cytoplasm tend to increase in HeLa cells, while the thicker nuclei have a tendency to increase in primary cultured mouse kidney cells. The fixation method did not affect these results.
These results indicate that the observations by differential interference and scanning electron microscopy agreed well in established cell lines, but did not in primary cultured cells.
Transmission electron microscopy of sections revealed that there were both types of nuclei, concave and convex, which supports the results obtained from the scanning electron microscopy. That nuclei appear either concave or convex in the surrounding cytoplasm is not an artifact but considered to be a physiological phenomenon related either to the cell cycle or cell establishment in vitro.

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