Page:Life in Motion.djvu/111

Rh this property of contractility. This statement, you will observe, explains nothing.

Muscular tissue is found in the body in two varieties of fibres which we term the smooth and the transversely striated. Those who examine with their microscopes the structure of the tissues of the body speak of minute things called cells. A cell is a little bit of living

matter, often having a membrane round it, and almost always having in it a small body, like a kernel, called the nucleus. Cells, always microscopic in size, so that many thousands might be packed away in a space the size of a pea, have many forms, as you see in these diagrams. Some are round, others polygonal, others elongated or drawn out, and others have little processes standing out from them. Now both kinds of muscular fibres are cells the bodies