HOW THE ANIMAL BODY IS FORMED II 



The ovum, known as the female egg, is composed 

 of the parts just described. If it is not fertilized 

 when ripe it passes away and dies. If fertilized in 

 a natural way, it enlarges in size and subsequently 

 divides into two cells; and these, passing through 

 similar changes, finally give rise to the various 

 groups of cells from which the body is developed. 



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 cer- 

 tain special kinds of work. In this way we have 

 various groups, with each group a community per- 

 forming 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 through- 

 out the body. 



Both individual cells and group cells are con- 

 cerned 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. 



A Word About the Cells. The cell always pos- 

 sesses its three parts membrane, protoplasm, and 

 nucleus. But there is no rule as to the size or 

 shape. Cells may be round or oblong, any shape. 

 Substances pass in and out of the cell walls; and 

 they are in motion, many of them, especially those 

 that line the intestines and the air passages, and 

 the white corpuscles of the blood. More than this, 

 some cells, Dr. Jekyl-like, change their appearance 

 and shape, send out finger-like bodies to catch 



