The hypothalamic neurosecretory cells of the rats, both the supraoptic and paraventricular nuclei were observed with the electron microscope.
It is interesting to note that the neuroscretory cells in both the nuclei frequently contain nucleolus-like bodies in the cytoplasm of their perikarya. The outline of such an inclusion body is much smoother and more regularly round or oval than that of the intranuclear nucleolus, and the diameter of the body is variable, reaching the maximal size of about 2.5μ, which is approximately the same as the maximal diameter of the true mucleolus. The ultrastructure of the inclusion body is quite akin in appearance to the intranuclear nucleolus, that is, the seeming constituent particles are lined up in beaded filaments or cross-striated bands. A close similarity between the ultrastructure of the inclusion bodies and that of the nucleolus strongly suggests the possibility that the inclusion bodies might be derived from the nucleolus. That corresponds to the light microscopic findings suggesting the extrusion of nucleoli in certain neurosecretory cells previously reported by many authors. The functional significance of the occurrence of such inclusion bodies is not clarified in the present study.

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The ovaries of normal mature virgin rats showing regular sexual cycle were fixed with osmium tetroxide, embedded in Epon 812 and then observed with the electron microscope.
The ovary consists of the germinal epithelium, follicles, corpora lutea and interstitial tissues. Along the surface of the ovary, the germinal epithelium consisting of a single layer of cuboidal or squamous cells covers the underlying connective tissue which is also called the tunica albuginea. Microvilli and stereocilia though in a lesser occasion can be observed extending from the free surface of the germinal epithelial cells. The adjacent epithelial cells are combined to each other by means of the terminal bars, directly below the cell surface. The intercellular space is usually dilated and filled with a liquid substance. A basement membrane is observed along the basal surface of the epithelium. Many pinocytotic vesicles are seen in the cell periphery of both the free and basal surfaces, and it suggests a possibility of the existence of active transport of some unknown substances through the germinal epithelium. The cytoplasm of the epithelial cell contains a relatively large amount of organelles, lysosome-like dense granules and keratin-like fibrils arranged in bundles.
The primary follicle consists of an oocyte and a single layer of flattened follicular epithelial cells surrounding the former. The oocyte possesses a nucleus with one nucleolus, a small amount of GOLGI apparatus, mitochondria and agranular vesicles. Free ribosomes and dense granules are also observed in the oocyte cytoplasm. Several mitochondria are arranged in a rosette around the dense core. The follicular epithelial cells of the primary follicle are flattened and poor in cytoplasm. Desmosome-like junctions are observed in places between the oocyte and associated follicular epithelial cells.
The oocyte of the secondary follicle shows a marked developement and differentiation of cell organelles. At the stage when the zona pellucida and follicular fluid begin to appear, many microvilli extend from the surface of the oocyte, and its cytoplasm contains a large amount of cell organelles such as cisterns of the agranular endoplasmic reticulum, mitochondria, GOLGI apparatus and multivesicular bodies. The follicular epithelial cells (granulosa cells) of the secondary follicles increase in number by mitosis. The cytoplasm of the granulosa cells is provided with relatively welldeveloped granular endoplasmic reticulum, a large amount of free ribosomes, and mitochondria with transversally oriented cristae. No agranular endoplasmic reticulum can be observed. Lipid droplets are occasionally contained in the cytoplasm. Several cytoplasmic processes arise from the inner-most layer of the follicular epithelium (corona radiata cells) and pass through the zona pellucida and attach to the surface of the oocyte.
The theca folliculi is obscure around the primary follicle, but it becomes clear around the secondary follicle. Two types of cells in the theca can be differentiated according to their morphology. One is the fibroblast which possesses a well-developed granular endoplasmic reticulum and free ribosomes. Another is the cell which has characteristics of the lipid- or steroid-producing cell, that is, the well-developed agranular endoplasmic reticulum, mitochondria with villiform cristae and a number of lipid droplets.
Lutein cells of the non-pregnant corpora lutea are provided with spherical nuclei each containing one or two nucleoli, well-developed endoplasmic reticulum of both the granular and agranular types, mitochondria with villiform cristae, many lipid droplets and several lysosomes. Some of the mitochondria attain to an enormously large size with ample villiform cristae and many intramitochondrial granules. Some other mitochondria may contain relatively large dense globules in the matrix.

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The additional fine structure of the canine olfactory hairlet is studied with the electron microscopy. The canine olfactory hairlet is unique in structure and it consists of four main portions, namely, 1. the basal body and its apparatuses, 2. the thick portion which is analogous to the mammalian epithelial cilia, 3. the transitional region where the nine peripheral doublets become single tubule and terminate abruptly leaving few single tubules, 4. the thin portion which has an ampullar structure on the midway and the tip where all the remainders of the hairlet tubules terminated finally. Their position in situ and their characteristic structure lead one to speculate upon their functional significance as a chemoreceptor. An atypical giant olfactory hairlet is found but its functional role is not known.

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In an attempt to study the effects of the gastric resection on the secretory activity of the gastric gland in the remaining stomach, the author observed the gastric chief cells of operated dogs.
The experimentai dogs were divided into 4 groups for the operation-the subtotal gasterctomy of BILLROTH I type (A-group), the subtotal gastrectomy of BILLROTH II type (B-group), vagotomy and hemigastrectomy of B-I type (C-group), vagotomy and hemigastrectomy of B-II type (D-group). From each group, four small groups were made, determined as follows, 1 week, 2 weeks, 1 month and 3 months after the operation. Dogs were killed and materials were taken at the periods of 1. before administration of food (unfed for 24 hrs.) and 2. 1/2, 1, 2, 3 hrs. after the diet. The vital fixation by LUNA's liquid and then the fixation by KOLSTER's liquid were employed, and the sections of the stomach were stained by HEIDENHAIN's iron haematoxylin.
The results obtained are summarized as follows:
1. In the group of the subtotal gastrectomy, the secretory activity of the individual chief cell is within the physiological limit, but the activity after the diet is irregular in BILLROTH I type while relatively regular in B-II type. It is so obvious in the group at the long term period after the operation that the different results between B-I and B-II type seem to be due to the difference of stagnation of food in the stomach.
2. The vagotomy induces no inhibition of the discharge of secretory vacuoles in the chief cells but brings about the irregular initiation of the secretory activity of the chief cells after the diet. The secretory activity of the chief cells after the vagotomy tends toward the production of the secretory substance in the cells.
3. The liquefaction (externally the vacuolization, preparation for the discharge) of the secretary granules produced in the chief cell is often prolonged or inhibited after vagotomy, and, not seldom, the functional figure of the cell seems to being outside of the physiological limit.
4. The general condition of dogs as regards to emaciation, vomiting and appetite is better in the vagotomy-group than in the others.
5. According to the experimental results of the author, the most favourable operation-results both with regard to the general condition and the secretory activity of the chief cells are found in the group of the subtotal gastrectomy with the gastrojejunostomy (BILLROTH II type).

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