An introduction to the study of cytology / by L. Doncaster.

  • Doncaster, L. (Leonard), 1877-1920.
Date:
1920
Catalogue details

Licence: In copyright

Credit: An introduction to the study of cytology / by L. Doncaster. Source: Wellcome Collection.

    24/352 (page 4)
    ality of cells is now being generally, if gradually, abandoned, it sometimes tends to reappear in the form that the nucleus is the fundamental and all-important entity, and that although the cell-protoplasm (“cytoplasm”) of the body is more or less continuous, the nuclei constitute distinct and independent units, in some way controlling and acting through the protoplasm which surrounds them, but all, to a large extent at least, unconnected with one another. This view has the advantage that it is not at variance with such obvious facts as the existence of multinucleate cells, and is supported by the usually sharply marked and definite char- acter of the nucleus, but it does not take into account the reciprocal relation that exists between nucleus and cyto- plasm. It also seems inconsistent with the fact that at times the nuclear substance may be more or less distributed through the cell, and that in the Protozoa at least a typical nucleus may be reconstituted from finely-divided fragments of nuclear substance to which by themselves it seems im- possible to apply the term nucleus. A great part of this volume will be devoted to the subject of the nucleus, so it will not be necessary here to say more than that this view does not seem adequately to meet the objections to the cell-theory in its older forms, and that it is probably better to regard not only cells but also nuclei as rather parts of an individual whole than to think of them as units out of which that whole has been built up. Even if the cell is no longer regarded as a fundamental unit in the composition of all living organisms, it is never- theless a convenient and quite natural conception, for the bodies of organisms consist of protoplasm, or its various products and modifications, in which are embedded nuclei, and each nucleus controls, or is in relation with, a certain amount of the surrounding protoplasm. The protoplasm