Various methods of changing the focal length on electron lens excited by permanent magnets are reported. The many new methods are proposed by the author and it is found that some of them are very useful in practice.
Stability of permanent magnet lens sysem against demagnetization; tempering effects, aging effects, resistance to magnetic field and variation of magnetic flux due to magnetic shunt and impacts are considered.
The high resolving power and easy maintenance of electron microscopes are proved to be achieved owing to the high stability of permanent magnet.

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Gomori's s-Collidine buffer was used with OsO₄ for tissue fixation for electron microscopy. It was found to be useful not only for fixation of general vertebrate tissues but also for that of embryological or invertebrate tissues. Method for use of s-Collidine buffer and some theoretical advantages over the other systems (veronal, phosphate, broate etc) were discussed.

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Exocrine cells of the carp pancreas were observed with the electron microscope.
1. This cell contains well developed endoplasmic reticulum of the rough surfaced type.
2. Zymogen granules are large electron dense spherical granules of about 2.5μ in diameter.
3. It is often observed that various sized spherical granules with similar density to that of the zymogen granule are enclosed within the sacs of endoplasmic reticulum. These may correspond to the so-called “intracisternal granules” of Palade.
4. The intracisternal granule of the carp pancreas is always a single spherical granule contained within a single spherical or elliptical sac of the endoplasmic reticulum. Apparent transitions between the intracisternal granules and the mature zymogen granules can be observed.
5. It may be considered that the rough surfaced endoplasmic reticulum may be closely concerned with the secretory activity in the exocrine cells of the pancreas.

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On the purpose of studying relationships of the fine structure to the function in the thyroid gland histochemically, various reagents were used as a fixative and their straining effects was observed electromicroscopically. Reagents used are as follows: Glyoxal, HgCl₂, Pb-acetate, KMnO₄, OsO₄.
The results obtained are summarized as follows:
1) When electromicroscopical specimens were fixed with glyoxal, HgCl₂ or Pb-acetate (isotonic sucrose solution, pH 7.4) the nuclear membrane, endoplasmic reticulum and mitochondria were clearly recognizable, their peculiar lamellar structure being preserved fairly well.
2) Fixation with lead acetate-glyoxal mixture caused deposition of somewhat coarse lead particles in the membrane of mitochondira and Golgi complexes, or on the border area of secretion granules while such a deposition of metal was observed neither in the fixation with lead acetate only, nor mercury salt (in glyoxal and formal aldehyde solution).
3) Permanganate (0.8% in isotonic saline) was also found effective as an electromicroscopical fixative or stain as osmium tetraoxide.
4) These-findings seem to suggest that the electron dense layer of endoplasmic reticulum, mitochondria or nuclear membrane is chiefly composed of proteins and fairly good preservation of their membrane structure by above mentioned fixatives is due to intermolecular bridge formed by the reaction of these reagents with -SH₂, -NH₂ or other functional groups of structural proteins.

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Etch pits in pure α-iron crystals after electroetching in Jacquet's solution under various conditions were observed in detail by means of electron microscope. The rows of pits along sub-boundaries are obtained in the small crystals existing in the large crystal, but not in the large crystals so far. The behaviour of the development of pits which distribute at random, on (011) surface of the large crystals is more complicated than that on (111) and (001) surface. The latter pits are surrounded by {011} plane and the former by both or either of {001} plane. The rhombic structure whose longer diagonal lies in ‹011› direction occasionally can be seen on the top of the pits on (011) surface. It is, also, confirmed that pits along slip lines contribute to surrounding carbon atoms around the dislocations.

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In order to prepare the replica of a surface of the material which is porous as well as very brittle, the specimen is usually embedded in some plastics and the replica must be taken in such state after an appropriate etching.
It has been investigated that the most suitable method to prepare the replica of a surface of carbon electrode and others. Various plastics were tested to embed the specimen. The etching method and the replica technique were also examined. It was found best to make replica by means of the method of three-stage replica, Methyl-cellulose-Ethylcellulose-Carbon, embedding the specimen in Methyl-methacrylate. Several surfaces cut out from a carbon rod in different directions were compared.
These techniques are also applicable for some porous materials as paper, wood and silk-fiber.

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This paper deals with an epoxy resin embedding method for ultrathin sectioning in electron microscopy.
The facts that the epoxy resins set uniformly with virtually no change of volume and without formation of bubbles indicate that the resins should be suitable for embedding media for electron microscopy.
The epoxy resins studied here are marketed under the trade name of Epon (Shell Chemical Co., U.S.A.).
The epoxy resins are a mixture of Epon 562 and Epon 815 that has the properties of liquids of low viscosity soluble in absolute alcohol.
After addition of an acid anhydride hardener, namely, dodecenyl succinic anhydride and an accelerator, namely, pyridine, the epoxy resins can be cured at 50°C to yield a solid block of the required hardness for ultrathin sectioning.
The hardness of the final block has been found suitable for sectioning material embedded in a mixture of Epon 562 and Epon 815 (in ratios of 2:85:5).

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A production of knives of good quality is absolutely necessary for the electron-microscopic investigations of the biological materials. The author devised a new method to meet this demand. The following is the essentials of the method. The glass-knife is made of sharp edge of two surfaces of this glass. The original glass plate has to be square (ca. 12×12mm²) with 5mm thickness. Cut-line is made on one surface diagonally with by a diamond cutter as shown in Fig. 1b.
The glass plate is cut into two pieces by heating the central portion on the microflame, holding the center of the glass plate on the flame for about 30 seconds.
A long sharp edge of glass is easily produced. Almost all glass-knives thus produced without special technique or difficulties are of good quality.

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