THE STORY OF THE BODY'S CONSTITUTION 7 



egg to the 1 -6,000th or even the 1-1 0,000th part of 

 an inch; dimensions 

 of these last found in 

 certain of the brain 

 cells. Other cells 

 (Fig. 2) may vary 

 from the 1 -200th 

 part of an inch in 

 diameter to the 

 l-25th part of an 

 inch; but all cells, it 

 will be understood, 

 are microscopic ob- 

 jects, and can only 

 be seen and studied 

 by the aid of a 

 microscope of fairly 

 high power (Fig. 3). 



Fig. 2. VARIOUS KINDS OP 

 BODY CELLS 



Including those found in mouth (F), 



windpipe (CD), digestive system (A), 



eye (B), and brain (E). 



ABOUT CELLS. The cell being thus a speck of 

 protoplasm is, in its essential nature, a living thing. 

 This fact must not be lost sight of, even with the 

 knowledge that cells undergo in the course of 



their development special 

 changes, many of them 

 dying and perishing, to be 

 replaced by other cells, 

 whilst others again may 

 become more or less 

 hardened and take part 

 in the formation of bodily 

 structures which can 

 scarcely be called vital in their nature. The cells 

 which compose the epidermis or outer layer of the 

 skin, for example, are produced from the upper sur- 

 face of the under-skin. As layer after layer of these 



Fig. 3.- GOBLET CELLS 



Found in the intestine or 

 bowel. 



