1) The author was able to demonstrate a nucleolar substance in mammalian nerve cells (spinal cord of rat, mouse, guinea pig, rabbit, dog and man) with his modification of the diphenylthiocarbazide (dithizide) method which had been introduced by Okamoto et al. (1942,1951).
2) By means of polarographican alysis of spinal cord, the author identified the dithizide positive substance with zinc. He consid e red that the substance may represent a protein-bound zinc.
3) At the post-natal stage (the 21,28 and 42 days a f ter birth), the dithizide positive substance appears not only in nucleolus, but also in nucleus and in cytoplasm. From several histochemical exami nations the nucleolar positive substance seems to differ from the cytoplasmic one.
Such diffe rence might be depend on the zinc-bound protein between the two. This observation seems to support Caspersson's theory (1950).
4) From the microscopic observations it was expected that the metal increases as the animal grows, but from the polarogram of the growing spinal cord of rat it was clear that the zinc concentration decreased with animal growth.

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1. In the normal course of the postnatal development of lymphoid organs in the rat, a remarkable transient elevation of the average number of mitochodria was observed in circulating lymphocytes, during the period between 4 weeks and 2 months after birth.
2. This period coincides with the period during which the processes of new formation and differentiation of Flemming's secondary nodules proceed in the mesenteric lymph nodes and splenic white pulp, the former in particular. After maturation of Flem - ming's nodules in these organs had been accomplished, the mitochondrial number in circulating lymphocytes considerably fell and did not rise agin.
3. These findings agree fairly well with the previous observations by Osogoeet al. (1953) and A way a (1956) on rabbits and provide further evidence to indicate that a marked rise in mitochondrial number in blood lymphocytes takes place as a consequence of extensive new formation of Flemmin g's secondary nodules in the lymphoid organs, which, in turn, indicates an increase in production and delivery of lymphocytes from these organs to the blood.

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The extrusion of nucleoli and their contents into the cytoplasm in the course of chromatolysis was studied morphologically, with spinal ganglion cells of dogs.
1) In the spinal ganglion cells sampled 3-8 days after recision of the sciatic nerve, pictures of nucleoli passing over into the cytoplasm were found in a rather high frequency. In such cases, it is rather rare to come upon a picture of a nucleolus In the moment passing through the nuclear membrane, but the author had the luck of finding some such pictures in this study, in which the nuclear membrane is perforated to the size of the nucleolus, of which a distinct trace was found left of its ejection into the cytoplasm. Seeing that such a trace was found fixed unobliterated in the specimen, we may assume that the transit of the nucleolus from within the nucleus out into the cytoplasm is rather rapid.
The extruded nucleolus would slowly collapse and their contents would diffuse out in the cytoplasm, in all probability. In the mean time, the perforated nuclear membrane is mended and in the nucleus the new nucleolus is found already in the course of regeneration.
2) In chromatolysis, small nucleoli (Heitz's so-called Nebennukleolen) were found often in the nucleus besides the originally existing single nucleolus. In such cases, similar small nucleoli were nearly always scattered in the cytoplasm too. Sometimes, pictures of such a small nucleolus just passing through the nuclear membrane into the cytoplasm were found.
3) Besides direct extrusion of the nucleolus, its content alone is sometimes discharged into the cytoplasm. In this case, the behavior of the Feulgen-positive substance in the nucleus comes into the question.
In chromatolysis, the Feulgen-positive granules attached to the nucleolus and the nuclear membrane are amplified and at the same time the Feulgen-positive threads stretched between the granules of both the sites show supernormal Feulgen reaction and come to be noted as distinct entities.
In methylgreen-pyronin stained preparations, sometimes, the outer surface of the threads are stained by methylgreen and the pyroninpositive substance jutting out from the nucleolus are contained inside them. This pyronin-positive substance extends the nuclear membrane and in some cases partly through the nuclear membrane to the surface area of the nucleus in the cytoplasm.
4) Sometimes again, th e nucleolus comes up to the internal surface of the nuclear membrane, as if fetched there by the Feuigenpositive threads. In such cases, the Feulgen-positive granule on the nucleolus and that on the nuclear membrane fuse together to form a broad Feulgen-positive mass at the point of contact, where the nuclear membrane is often caved in to the side of the nuclear plasm. The pyronin-positive substance of the nucleolus is frequently found discharged through the nuclear membrane into the cytoplasm at the point of contact of the nucleolus and the nuclear membrane.
5) In chromatolysis, the extrusion of the n ucleoli and their contents seems to have its significance in supplementing the cytoplasmic nucleotides depleted by the collapse of the Nissl bodies.

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