The Animal Cell

The Animal CellThe essential constituent of all living matter is protoplasm, a translucent jelly-like material of complex structure. Its chemical composition cannot be determined by ordinary methods of analysis, since these inevitably entail the death of the protoplasm.

The analysis yields a certain amount of information regarding the ultimate elements of which protoplasm is composed, but a knowledge of the manner of combination of these elements into definite compounds can only be obtained by observing the behaviour of protoplasm during life towards other chemical materials.

When studied in this way, it soon becomes obvious that protoplasm cannot be regarded as a single definite chemical compound, but rather as a series of unstable, ever-varying groups, holding together under certain physiological conditions, but readily splitting asunder when these conditions alter.

In the animal body the protoplasm is divided up into small individual units known as cells. In the higher organisms these cells vary much in form and function, but all possess certain features in common. The main structural components of an animal cell are : (1) Protoplasm, (2) A nucleus; but in addition there are present in the more complete cells, (3) A nucleolus, (4) Centrosomes and attraction spheres (Fig. 1).