The mitotic cycle : the cytoplasm and nucleus during interphase and mitosis / by Arthur Hughes.

  • Arthur Frederick William Hughes
Date:
1952
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The mitotic cycle : the cytoplasm and nucleus during interphase and mitosis / by Arthur Hughes. Source: Wellcome Collection.

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    the mitotic cycle the basophil granules of the cytoplasm, the 'chromidia', had dis¬ appeared. These bodies must therefore be related in composition to nuclein. A similar treatment of sections of the intervertebral ganglia of the cat resulted in the dissolution of the Nissl granules. The demon¬ stration that nucleic acid is found in the cytoplasm is thus nearly forty years old. In van Herwerden's experiments, the changes within the oocyte nucleus, either in the chromatin or the nucleolus were very much less marked. He returned to this subject in a further study (van Herwer- de№^) of the effects on the sperm head of both nuclease and i per cent hydrochloric acid. He found that in both fishes and echinoderms the basophily of the sperm nucleus was decreased after hydrolysis by the latter reagent in the cold, but that the mammalian sperm was resistant to this treatment. The same result was obtained in each case by digestion with nuclease. Van Herwerden saw in his results an illustration of the observations of Kossel^^ and Kossel and Edlbacher^® that the linkage between the basic protein and nucleic acid was broken with particular ease in the sperm nucleoprotein of fishes and echinoderms. He further observed that the unripe mammalian sperm head was attacked by the agents which he employed. We now know that it is the difference between the nucleic acids of the sperm head and of the egg cytoplasm which is primarily responsible for van Herwerden's results. At the time, the conclusion was drawn from these results that the 'nuclease test' could not be used as a reliable index of the presence of chromatin. The verdict of Wilson^® on this matter, still to be found in the third edition and its reprints is that 'it must be admitted, therefore, that we have no certain means of identify¬ ing chromatin in the cell apart from its morphological history'. CH — CH I I CH GCHO \ / О (i) Furfural СНз—CO—CHj—CHj- COOH (ii) laevulinic acid HO—CHCO • CHCH, • CHO (iii) CD. hydroxy laevulinic aldehyde Figure i—Structural formulae The recognition of two classes of nucleic acids preceded this cyto- chemical work of van Herwerden by many years, but until long after this period it was believed that one was found in plants and the other in animals. In 1893 Kossel^^ had shown that although nucleic acids from both yeast and animal sources contained the same purine bases, the 4