The Animal Body a Group Collection.
—The body is, therefore, a mass of cells; not all alike, of course, but grouped together for the purpose of doing certain special kinds of work. In this way we have various groups, with each group a community performing its own function. The brain forms one community; and these cells are concerned with mind acts. The muscle cells are busy in exerting force and action. Another group looks after the secretions and digestive functions, while another group is concerned solely with the function of generation and reproduction. And so it is throughout the body.
Both individual cells and group cells are concerned with disease. One cell may be diseased or destroyed, but the surrounding ones may go on just the same. It is when the group is disturbed that the greatest trouble results.