Laboratory work in bacteriology / by Frederick G. Novy.

  • Novy, Frederick G. (Frederick George), 1864-1957.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Laboratory work in bacteriology / by Frederick G. Novy. Source: Wellcome Collection.

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    The hig-her animal and plant cell always contains a nucleus within the protoplasm. The nucleus unquestion- ably plays a most important part in the division of the cell. So much so that it has been considered essential to repro- ductive changes. Inasmuch as bacteria possess the power of multiplication, it might be expected that they would contain, like higher forms, a well defined nuclear body. The direct examination of a bacterial cell fails to reveal the presence of any form analogous to a nucleus. Usually, the cell appears perfectly homogeneous, and the closest examination will not bring out a structure. The question of the existence of nuclei in bacteria has been the subject of numerous extensive investigations which have led to very different conclusions. In fact, it may be said that the presence of a nucleus is not demonstrated. There are some who consider bacteria as wholly devoid of nuclei. The minute granules which are not infrequently present, especially in older cells, are believed by some to be the first indication of the formation of a nucleus. Some have endeavored to show the existence of a cen- tral body which, while it is not a nucleus in the sense that this term is usually employed, nevertheless possesses certain properties of a nucleus, and may therefore be considered as a rudimentary form of that body. On the whole the opinion prevails that bacteria consist essentially of nuclear matter surrounded by a very thin protoplasmic layer and by the cell-wall. It is well known that in embryonic cells the nucleus almost fills the cell. This view is especially strengthened by the behavior of bacteria to anilin dyes. The bacterial cells stain readily and intensely, like the nuclei of higher cells. This is assumed to be due to the presence of similar chemical sub- stances such as nucleins. The presence of a nuclein com- pound in the bacterial cell is indicated by the fact that nuclein bases and even a protamin-like body have been isolated.