On the structure and growth of the tissues, and on life : ten lectures delivered at King's College, London / by Lionel S. Beale.

Date:
1865
Catalogue details

Licence: Public Domain Mark

Credit: On the structure and growth of the tissues, and on life : ten lectures delivered at King's College, London / by Lionel S. Beale. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    properties to those wliich their progenitors possessed. Various theories have been proposed from time to time with the view of rendering the description of structures as simple and as intelligible as possible, and for the purpose of furnishing us with some general notion of the manner in which tissues are built up in living beings. The principal of these is that known, as I have no doubt you are aware, as the Cell-theory. It was supposed by its originators, Schwann and Schleiden, that all organized beings are developed from cells, and that in those higher creatures whose organisms consist of various tissues differing re- markably from each other in appearance and structure, the differences are caused by certain modifications occurring in the course of the development and growth of the con- stant structure, the cell. Now, a cell is a smaU body vary- ing, according to circumstances, in shape and size, but for the most part of a round or oval form, and consisting essentially of a clear transparent membrane in the form of a minute sac closed at all points, and enclosing certain contents. The cell during some period ^f its life contains another small body, either lloating free within it or attached to its internal surface, and this is called a nucleus, and sometimes, though not invariably, in this nucleus may be seen a minute particle which is called a nucleolus; so that if I were to represent roughly the structure of a cell on this board, we shall have a figure somewhat of this sort. Ex- ternally a delicate membrane enclosing certain contents, which vary in different cases, but I will represent the cell as it appears in its most distinct form. [Diagram of the ceU on the board.]