In all mammals described i n this report, the masseter consists of the proper masseter group which includes the first superficial, second superficial, intermediate and deep masseters and the improper masseter group which consists of the maxillo- and zygomaticomandibular muscles. These muscular elements can be identified exactly in every animal investigated. The special features are described as follows:
1) In the red kangaloo, the first superficial, second superficial and intermediate masseters are thin, though broad. The deep masseter group makes especially a good development, namely, the pars anterior is identified in the first and second layers and the pars posterior can be divided into the first-fifth layers. The improper masseter group which includes the maxillo- and zygomaticomandibular muscles makes a good development, which is comparable to those of the carnivorous animal.
2) In the primate, the t r ansitional change of the zygomaticomandibularis from the zygomatic arch to the supraorbital torus is pursued from the lower to the higher forms. In the galago, the muscle takes its origin from the zygomatic arch. In the squirrelmonkey, it originates not only from the zygomatic arch, but also spreads over the superficial temporalis, making the semicircular plate. In the chimpanzee, the muscle spreads between the superficial and deep temporales, connecting the lateral portion of the supraorbital torus with the coronoid process as in the human masseter.
3) The masseter of the guinea pig makes a complicated development. The first superficial masseter is divided into the pars anterior and pars posterior. The former corresponds to the pars reflexa (Tullberg), bifurcating into two branches. The maxillomandibular muscle consists of two parts as in the rat (Yoshikawaetal.,1961). One of them passes through the infraorbital foramen and the other originates chiefly from the zygomatic arch and terminates in the long sulcus in the mandible. The latter corresponds to the zygomaticomandibularis after Toldt (1905), Schumacher (1961, b) and Schumacher-Rehmer (1962). The real zygomaticomandibular muscle is vestigial as in the rat (Yoshikawa et al.,1961). It develops between the posterior part of the zygomatic arch and the root of the glenoid process.
4) In the bear, the maxillo- and zygomaticomandibular muscles make a specially good development. In the adult form, the former reflects under the second superficial masseter, taking the anterior position to the intermediate masseter. The pars posterior of the deep masseter makes the well developed pyramidal form with rich tendons, the lamination of which, however, cannot be followed.
5) In the Indian elephant, the development of the maxillomandibular muscle is remarkable as in that of the horse. The pars anterior of the deep masseter cannot be identified.

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In male mice of an inbred Japanese strain (dd), effects of hypophysectomy on the thymus were studied on a weight basis. Hypophysectomy caused enlargement of the thymus, both in immature males of 30 days and mature males of 170 days of age. The cause of the thymic enlargement following hypophysectomy was discussec in relation to the trophic, particularly gonadotrophic, hormones of the hypophysis.

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Adrenal glands from three aged cows (Japanese Native Cattle)were studied histologically. Animals were 28,21 and 17 years old, respectively.
A remarkable reduction in nuclei density of the outer z. fasciculata as well as the inner z. fasciculata was noted. The data presented here showed highly significant differences between the young and aged cows.
The z. glomerul o sa was most severely affected among the cortical zones in respect to the advancing age. Those enumerated in the z. glomerulosa are, lipid deposition and pigment cells in both the stromal and the parenchymatous tissue. The pigment granules of parenchymatous cells seem to probably be the degenerative material of cell nuclei.
A regional disappearance of the z. glomerulosa was considered as one of the striking change. An appearance of a dense fibrous layer between the z. glomerulosa and the z. fasciculata was discussed from the viewpoint of the downgrowth of cortical cells. Those changes described here would probably imply a reduction in activity of this zone.
The fasciculata cells were much reduced not only in number but also in size. Lipid deposition and dilated sinusoids were also remarkable. Those changes enumerated in the z. fasciculata would probably imply a reduction in activity of this -zone. Fibrotic or hyalinized areas were frequently found within the z. fasciculata.
An extensive appearance of granular cells in the outerz. fasciculata was one of the most striking changes. Characteristics of the cytoplasmic granules were quite similar as those in glomerulosa cells as far as methods used and the functional significance of these granular cells was discussed.

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The mucous membrane of the human small intestine and appendix were fixed in 1% osmium tetroxide buffered with veronal acetate (pH 7.25), embedded in styrene-methacrylate and, after sectioning, stained with sodium hydroplumbite for electron microscopy. The results obtained are as follows:
1. Nerve bundles entering the mucosae of the human small intestine and appendix divide into many fine branches, each consisting of several axons with a Schwann cell sheath covered with basement membrane. Each axon is usually hung by one mesaxon,108Nerve Endings in Mucous Membrane of Human Intestine 419. but sometimes two or more axons are held in common one and the same mesaxon.
2. As the fine nerve bundles pass into the muscularis mucosae,. some of the axons in the nerve bundle lose the covering of the Schwann cell and are markedly swollen to form the vesiculated nerve processes which lie along the outer surface of the fine nerve bundle and are filled with a large number of agranular synaptic vesicles without granules, several granular vesicles containing dense granules and mitochondria. A large part of the surface of the vesiculated nerve process is naked and shows juxtaposition to the smooth muscle cells at a relatively large distance of 2,000 to 3,000 Å, The vesiculated nerve process of this kind would represent the possibility of presence of the diffuse innervation in the muscularis. mucosae by ' Synapse auf Distanz ' suggested by Jabonero.
3. In the propria of mucosae the fine nerve bundles lie between the vessels, intestinal glands and proper cells. The fine axons in. the nerve bundle lose their sheath and pass into grooves on the surf ace of the interstitial cells of Cajal to form slightly swollen expansions which contain many agranular synaptic vesicles. Vesiculated nerve processes of this kind involve a close apposition of the surface membrane of the nerve process and that of the interstitial cell. They are separated by an interval ranging from 120 to-200 Å in width and show an increased density in the contiguous. field of the synaptic junction. The agranular vesicles appear as a cluster polarized toward the closely apposed synaptic membranes.. Basement membrane material does not extend into the cleft of this. type of synaptic junction.
4. The nature of both types of vesiculated nerve processes. found here with reference to the transmitter substances, acetylcholine and catechol amines, which are thought to be related to tha agranular and granular synaptic vesicles respectively, are briefly discussed.

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Chromosomes of 8 normal chorionic villi,15 hydatidiform moles,6 destructive moles and 4 chorioepitheliomas were studied. Normal chorionic villi were characterized by either normal male or female diploid cells with a sharp mode. Two hydatidiform moles were provided with triploid cells. The remaining 13 hydatidiform moles showed a modal number of 46 with frequent occurrence of tetraploid and aneuploid cells. Destructive moles showed a decrease of orthoploid cells with a marked occurrence of aneuploid cells. In chorioepitheliomas, aneuploid cells were consistently predominant in cell population. Possible inference was induced that aneuploidization of chromosomes seems to play a significant role in the malignant transformation of cell population.
Acknowledgement: The authors are very grateful to Dr. Motomichi Sasaki for his friendly assistance in preparing this manuscript with expert advice.

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In the laboratory dissection for medical freshman, a non-rotation of the midgut loop was found peculiarly in association with the open-left supracolic peritoneal recess and poorly developed bur sa omentalis. Although the non-rotation itself is not of very rare occurence, such a combination of three peritoneal abnormalities deserves attention, implying that some common factors may have induced these developmental anomalies of the intestine and peritoneal garnitures.
Acknowledgment. The author is grateful to Mr. Y. Fukuda, the technical assistant, for his fine work of photography.

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Micrurgical studies were made on the Golgi complex in the living cultured cells under the phase microscope. The Golgi complex, which is a cluster of filamentous or membranous elements with illdefined contour in the living cell, increases in contrast as the nuclear membrane, nucleolus, mitochondria and the other cytoplasmic inclusions accentuate visibility, when death changes are elicited by severely injuring the cell. The Golgi complex then appears like a cluster of phase-dark threads which entirely fill up the Golgi area. These threads are optical sections of membranous structures, most of which are arranged parallel to the nuclear membrane and are seemingly anastomosed with one another with processes.
Micro-operations could be made on cells wh i c h were assuredly living during the course of treatment in view of their appearance under phase contrast and of their reaction to stimuli. The operations with the tip of a microneedle of gently stirring the Golgi area, of providing a scar in the same area, and of introducing a lipid droplet in and out of, the Golgi area prove that the ground substance in which the Golgi complex is embedded is of the same physical state as the general cytoplasm, i. e., it is like a soft jelly in consistency, and that the Golgi lamellae are not fragile but flexible and elastic ones.

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The fish hybrids, Gnathopo g on elongatus elongatus _??_× Pseudorasbora parva _??_ and the reciprocal, show a type of the external form of the brain intermediate between that of both parents. This phenomenon seems to have a relationship to the degree of the development of the barbels and the sexual behavior which are intermediate between those of the parental species.

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Observations on epoxy r esin embdded sections of tissue mast cells of the iris of Triturus pyrrhogaster (Boie) revealed the following additional findings to our previous study on methacrylate embedded sections.
1. The vacuoles frequently seen within the middle disk of light cell type mast cells in methacrylate embedded sections do not appear so often in epoxy resin embedded sections, therefore rather some of them are thought to have been the result of sublimation by electron beam. Further, there is a localized swelling of the low density layer of the middle disk with decreased density of the high density layer passing through this area and this may be the primary step of the process of vacuole formation resulting in the separation of the middle disk.
2. The dark colored granules, which predominate in the dark cell type mast cell, initially consist almost entirely of matrix of high density and a definite middle disk is gradually formed in the matrix. With the maturation of the granule, there occurs a marked reduction of the density of the matrix, probably due to liquefaction, and an increase of volume. Occasional fusion of granules may occur due to the partial disappearance of the limiting membrane. On the other hand within the middle disk, swelling develops with separation and the middle disk gradually dissolves and disappears in the liquefied matrix. In other words, with maturation of the granules, there is a transition from dark cell to light cell.
3. Occasionally, cylindrical or scroll-like lamellar structures appear within the matrix of light cell type mast cells but these were seen previously in immature mast cells also and are presumed

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Using spread-preparations stained with toluidine blue buffered at pH 3.2, the mast cells in the peritoneum and mesentery of adult Triturus pyrrhogaster (Boie) were observed.
1. Inside the capillaries, there are mainly the mulbeery-form mast cells filled densly with bluish purple granules, and the occasional immature mast cells in which both metachromatic and orthochromatic smaller granules are loosly mixed.
2. Outside the capillaries, there e x ist, besides the same sort of mast cells as seen inside the capillaries, other large mast cells in which granules are bigger and reddish purple and occasionally some of them are dispersed out of the cell bodies, and few remarkable dendrite-type specific mast cells.
3. The latter extend the l o ng dendrite-like, snaked processes filled with smaller, metachromatic granules in all directions, and tend to anastomose each other to form an extensive network. And they are distinguished from the ordinary type mast cells not only in their shape but also in the size and stainability of the nuclei and the size of the granules.
4. The mast ce l ls seem to be the ones which emigrated from other regions by the capillaries and were full growth there.

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Examining several new stains for elastic fiber the author found the superiority of the aldehyde-thionin and victoria blue methods. The aldehyde-thionin or victoria blue method by which we could stain electively not only the elastic tissue but also several kinds of cell and tissue after performing the tissue oxidation, are combined with some other dyes. Using this property, the author devised some excellent methods for routine stain to be applied to many kinds of tissue sections.

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The behavior of the RE cells lining the sinusoidal walls in the bone marrow and liver has been studied after a single intravenous injection of a sublethal dose of Merk's saponin (abou t 3 mg per kilogram of body weight) into adult rabbits. In order to visualize the RE cells and to facilitate observations, a large amount of India ink was injected intravenously 30 minutes before autopsy.
It has been found that the RE cells lining the sinusoidal walls in red bone marrow and liver are damaged to a large extent by the cytolytic action of saponin and the sinusoidal walls have once disappeared partially or completely within 24 hours after saponin injection. Regeneration of the RE cells, leading to the reappearance or restitution of the sinusoidal walls that have once disappeared, has been accomplished during the period from 5 to 14 days after saponin injection.

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1. The accessory optic system in the rabbit was studied by means of Marcia technique.
2. Four group s of retinal fibers were recognized to terminate in the hypothalamus or in the ventral tegmental area of the midbrain, i. e.1) preoptic component,2) supraoptic component,3) anterior accessory optic tract,4) posterior accessory optic tract.
3. The preoptic component is composed of a s m all number of uncrossed retinal fibers, leaving the optic nerve at its mediodorsal corner just rostral to the chiasm to descend dorsolaterad almost in parallel with the dorsal surface of the chiasm to finish its course partly in the lamina terminalis and partly further caudally in medial preoptic area. Fibers show no sign of crossing.
4. The supraoptic component is com p osed of a small number of crossed retinal fibers diverging from the dorsal surface of the chiasm to terminate directly in the pars dorsolateralis of the supraoptic nucleus.
5. The anterior accessory optic tract is composed of the retinal fibers which cross in the chiasm most posteriorly. It appears first medial to the main optic tract on the ventral surface of the diencephalon and then more caudally is divided into a lateral and a medial groups by the medial end of the cerebral peduncle. The lateral group penetrates dorsad through the interfibular spaces of the cerebral peduncle to terminate in the subthalamic nucleus and some of them diverge more caudally into the substantia nigra. The medial group finds its termination in the lateral hypothalamic nucleus and in the pars ventromedialis of the supraoptic nucleus. Sparse fibers are seen to enter the subthalamic nucleus by swinging around the lateral margin of the cerebral peduncle from the lateral group and by swinging around the medial margin from the medial group.
6. The posterior accessory optic tract is composed of the crossed retinal fibers first diverging from the superior quadrigeminal brachium to travel along the lateral surface of the diencephalon and then obliquely along the ventral surface of the cerebral peduncle to arrive at the medial end of this where it turns dorsolaterad along the medial margin of the cerebral peduncle to enter the nucleus opticus tegmenti of Tsai ('25). From the terminal part of this tract in the midbrain tegmentum some fibers are given anterolaterad into the substantia nigra (pars reticularis), a few of which pass into the subthalamic nucleus.
7. It is shown that both the anterior and posterior accessory optic tracts find termination in the subthalamic nucleus and in the substantia nigra, thus establishing the connection between them.
8. The retino-hypothalamic connection is not unitary. The hypothalamus (anatomically and functionally referred to as the SPH-system, Ban '62, '64) receives optic fibers by way of the preoptic component (uncrossed fibers), supraoptic component (crossed fibers) and anterior accessory optic tract (crossed fibers). This is summerized as follows; the retinal fibers terminate in the medial preoptic area and nucleus supraopticus (of the area sympathica-B, )and in the lateral hypothalamic nucleus (of the area parasympathica-C of the SPH-system of B a n, '62, '64).
9. Each retinal quadrant has a share in the composition of the accessory optic system almost in equal quantity and distribution of fibers except in the case of the preoptic component, so far as observed in the series of our frontal sections. For the preoptic component, fibers from the medial or lateral quadrant were observed a little more in number than those from the superior or inferior quadrant.
10. Marchi findings in rabbit were compared with Nauta findings of previous authors in the same animal with consideration of merits and demerits of Marchi technique itself.

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The phosphatase activities in the proximal tubule cells of the rat kidney were examined with light and electron microscopes. The brush border shows a strong reaction product using ATP and β-glycerophosphate, while the infolding plasma membrane shows little sign of the activity. The tubular invaginations and vacuoles also show the reaction product incubating ATP or alkaline phosphatase medium. Large granules identified as lysosomes which appear to coalesce with the vacuole possess acid phosphatase activity. No cytochemical relationship between Golgi complex and lysosomes is observed.

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The intralobular nerve fiber and probable nerve terminal on the liver parenchymal cell were observed in the mouse liver, and their fine structure was described as revealed by electron microscopy.
The possible nerve terminal is naked without covering Schwann cell and contacts with the liver cell directly. The nerve terminal usually locates in the indentation of the cell surface or embedded in the liver cell cytoplasm separated by a distinct plasma membrane. The terminal is characterized by accumulated mitochondria, dense granule and vesicles. Some of the vesicles contain a dense core.

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The fine structure of the intestinal epithelium in the lamprey was studied by electron microscopy. The simple columnar epithelium of the lamprey intestine was composed of three different kinds of epithelia; the striated border cells, the secretory cells, and th e ciliated cells. The striated border cells were most numerous and common throughout the entire intestine, and frequently showed numerous small vacuoles containing less dense materials which gave PAS positive reaction in the apical cytoplasm. The secretory cells, the cytoplasm of which was packed with particularly well developed granular endoplasmic reticulum and free RNP particles, were seen sporadically among other cells and, in all cases, showed numerous small granules, probably zymogen granules, in the tapered luminal cytoplasm. The ciliated cells were found sporadically or grouped between other cells.
The study s uggested that the striated border cells are both absorptive and secretory in function, the secretory cells are concerned with the secretion of enzymes necessary for intestinal digestion, and the ciliated cells are important for the transport of food materials in the lumen of intestine because of weak peristaltic action in the lamprey intestine. The morphological and functional significance of these three kinds of epithelia in this primitive vertebrate was discussed from the view point of evolution in vertebrate.

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The histochemical distribution of unspecific alkaline phosphatase in two human embryos in Streeter's horizon xii has been presented. The highest activity of the enzyme is observed in the neural tube, the floor plate regions of the mid- and hindbrains and the spinal cord exclusive, the lung bud, the thyroid diverticulum, the cloaca and the primordial germ cells. Those showing moderate reaction are the proximal parts of the neural crests, the auditory vesicle, some epibranchial placodes, major part of the gut, the myo-dermatomes of the somites, some parts of the coelomic epithelium and some of the nephric structures. A specific suppression of the enzymatic reaction is discernible in the floor plate of the neural tube, the peripheral parts of the neural crests, the esophagus, the liver primordium, the sclerotomes and the caudal part of Wolffian duct. In addition, this stage is characterized by the following facts: the formation of the acoustic nerve from the auditory vesicle takes place; the facial and glossopharyngeal placodes are established as the thick, highly phospbatase positive areas of the integumentary ectoderm; the production of the primordial germ cells extends to the coelomic epithelium from the hindgut epithelium; the vascular endothelium becomes phosphatase positive.

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In embryonic development, myelinization on the perikarya of the eighth cranial nerve ganglion cells is first observed in about-17-day chick embryos. It progresses, gradually increasing both thickness and compactness of each sheath as well as number 'of myelinated neurons. The well-developed myelin sheath, however, does not occur until about 3 days after hatching. A few myelinated fibers are contained in the eighth nerve of 13-day chick embryos already.

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The auxiliary cells, i. e., the nurse cells in the ovary of the sea urchin species,Hemicentrotus pulcherrimus and Heliocidaris crassispina at the early stage of oogenesis served as materials and investigated with particular reference to the glycogen particles by means of light and electron microscopy.
At the beginning of oogenesis in the ovary, the nurse cells show a peak of their development and a positive Pas-reaction. Thereby, the cells are arranged closely being partly connected with the “septate desmosomes” of Wood ('59) and filled up with large numbers of glycogen particles accompanying among them a small number of oil droplets and mitochondria, but few of endoplasmic reticulum and of other organoids and show almost no sign of glycogenesis. Of these cytoplasmic structures, the glycogen particles are identified as a particulate form of glycogen because of their variability in sizes, density as well as affinity for lead hydroxide and others, as recently Reveletal. ('60) noted. The glycogen particles in the present case are of ca.400-600 Å in diameter and of generally spherical or multiangular in shape but associated with no membraneous superficial structure. On the contrary, within the moderate dense amorphous ground substance of the particles a small number of fine particles of high electron density in ca.30-50 Å diameter i. e., the “elemental particles” are perceived.
With the progress of oogenesis in the ovary, however, the nurse cells begin to retract gradually and the glycogen particles in the nurse cells become dissolve to be discharged lastly from the cell surface into the intercellular space. Thereby, on the one hand, the glycogen particles appearing in the superficial cytoplasm begin to fall into a glycolysis being taken up into the small vesicles immediately beneath the plasm membrane and discharged through the cell surface. On the other hand, the other abundant glycogen particles in the deeper cytoplasm become to be broken down to make large dense aggregates of the “elemental particles ” from the glycogen particles. Among the “elemental particles ”, however, the ground substance of the glycogen particles become to dissolve and coalesce to make the ground substance of the large granules, into which a small number of “elemental particles ” right above noted, become to be arranged in concentric lamellar or whirl-like structure of less electron density.
In addition, in the deeper cytoplasm one can perceive often a region with “ heterolamellar structures ” where a few of mitochondria are surrounded with layered and flattened membranes to be swollen to make a large vacuole, containing probably a kind of nutrient substance.

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Using quantitative metho d the cellular density in the bone marrow, the weights and the total number of nucleated cells in the total marrow of the whole body were estimated in the normal rats from 1 week to 18 months of age. These average values are shown in Table 1. The data indicate that an active hemopoiesis occurred between 2 and 4 months of age.

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The eosinophil leukocytes of fishes contain no peroxidase activity while, in general, those of animals higher than fishes, are peroxidase positive. However, there are exceptions to these general findings as follows: 1. Although the eosinophil leukocytes of American urodeles such as Triturus viridescens viridescens and Pseudotriton ruber, are peroxidase positive, those of many other urodeles examined are peroxidase negative.2. In reptiles, only the eosinophil leukocytes of the Trigonocephali and the Gecko japonicus are peroxidase negative.3. In these exceptional cases, however, the neutrophil leukocytes are generally intensely peroxidase positive, suggesting that there is a dissociation in hematopoiesis between eosinophil leukocytes and neutrophil leukocytes.
In electron micrographs of the eosinophil leukocytes in the penhepatic zone zone of Triturus viridescens viridescens, the reaction products of peroxidase activity were evidenced in the form of dense material localized in the eosinophil granules in the cytoplasm. Neither mitochondria nor any other components in the leukocyte showed increases in density. The eosinophil granules of the salamanders such as Triturus viridescens viridescens, Ambystoma maculatum and Triturus pyrrhogaster did not possess an internal structure comparable with the central core of the human eosinophil granules.

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1. When repeated administration of morphine is given to rats, weight gain is inhibited and the volume of urine increases in quantity.
2. In morphinized rats, Gomori positive granules in the hypothalamo-hypophysial system shows a decrease or they becomes scarcely observed.
3. When withdrawal of morphine administration is made in morphinized rats, the volume of urine begins to decrease on the next day, shows the utmost decrease on the 3rd day and after that it gradually increases. At the same time Gomori positive granules in the hypothalamo-hypophysial system begin to gain in quantity on the 1st day and the neurosecretion shows a remarkable increase on the 3rd day to the 5th day, then it decreases again.
4. In morphinized rats, ADH content in the hypophysis and serum decreases, but when withdrawal of administration is made they show an apparent increase on the next day.
5. It is considered that repeated administration of morphine inhibits the neurosecretory activity of the supraoptico- or paraventriculo-hypophysial system, reduces production of ADH and increases the volume of urine, and that at withdrawal of morphine the activity of the neurosecretory nuclei accelerates as a reaction and urine diminishes rapidly in quantity in company with rapid production of ADH.

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After observation through the electron microscope of the proximal tubule cells of the domestic fowl, pigeons, and lovebirds, the author arrived at the following conclusions.
1) The fundamental structure of the proximal segments of these three birds were very similar.
2) Proximal segments might roughly be divided into the neck portion, the pars convoluta and the pars recta.
3) The most important point of structural difference between the avian proximal segments and mammalian proximal segments was the structural difference of the, plasma membrane system, especially the basal and lateral cytoplasmic membrane.
4) Typical desmosome could not be seen in the junctional region of the avian proximal segment.

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