Outlines of scientific anatomy : for students of biology and medicine / by Wilhelm Lubosch ; translated from the German by H.H. Woollard.

  • Wilhelm Lubosch
Date:
1928
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of scientific anatomy : for students of biology and medicine / by Wilhelm Lubosch ; translated from the German by H.H. Woollard. Source: Wellcome Collection.

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    position, it can scarcely be doubted that there are qualitative changes of the chromosomes which must have a pronounced effect on the unfolding of form. This would be the unfolding of the G of the reaction formula to a Gj [para. 32] ; how and under what conditions this follows cannot be stated at this moment. “ In itself,” the process appears so little like any other organic process. Since the nucleus stands in such intimate relation with the plasma, nutritive influences in the widest sense, as Weismann already implied in his theory, must be made answerable for this, as well as crossing over with the ensuing changes in the inner constitution of the chromosomes. Still more difficult is it to answer the question “ when.” The most likely idea is that there may be a time when the germ cells within the body are open to somatic influences. The time of the growth of the ovum and its maturation have long been regarded as periods of finely divided chromatin and therefore of account (Lubosch 1902). It has been shown since, experimentally, that this period is indeed a “ sensitive period” in the sense that during it the germ cells can be influenced by exogenous events hereditarily. (Standfuss and Fischer in butterflies, and Tower in the Colorado cockchafer.) Under parallel induction (Detto) one understands the process by which a stimulus works on the body and the germ cells at the same time whilst most recently it has been shown by Stieve that also through stimuli, which only work on the body, the germ cells may be affected harmfully along with the body. Naturally it has not been proven that these changes of the germ cells are at the same time a change of their constitution, yet they do show a way in which such changes may arise. The connection with the above problems [para. 34], in particular to the conception of an unfolding of the germ-plasm following orthogenetically under the influence of stimuli, is given here. In particular after all we now know on structure, form, and form formation and the inner constitution of the chromosomes we are correct at this time in distinguishing sharply between these forms and the hypothetical form of the germ plasma. The chromosome itself, whose capacity for change occurs not only in different phases of cell life, but also in the development of the species, cannot be the final element in the formative processes. It is itself only a “phenomenon,” a “momentary form” (Fick), at every moment governed by constitutional and functional factors of the whole condition of the nucleus. A water turbine arranged for the watering of garden-beds is an intelligible example of how a large structure can be only a momentary form of what apparently works on a complex combination of structure
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