STRUCTURE OF A CELL 



45 



Cell from 

 mouth,with 

 stained nu- 

 cleus. 



substance, somewhat like white of egg in consistency. Under the 

 microscope it seems to be either granular or made of tiny bubbles 

 floating in a more fluid medium, or it sometimes appears to be 

 made up of delicate fibrils or threads, forming a network of infinite 

 complexity. But it is always found making up the structure of 

 living things, just as bricks make up the structure of 

 a wall or a house. 



Structure of a Cell. — One of the easiest ways to 

 obtain cells from your own body is to wash your 

 hands carefully and then scrape the inside of your cheek 

 with your clean finger nail. Place a tiny bit of the 

 scrapings on a glass slide, add a drop of dilute blue 

 fountain pen ink, place a cover glass ovsr it, and examine with a 

 microscope. You will find a number of cells, more or less rounded 

 in appearance, and more or less stained by the blue dye. A care- 

 ful examination will show three distinct parts : an outer covering, 

 which is the cell membrane, the cell body filled with protoplasm, 

 and a more deeply stained portion of the protoplasm called the 

 nu^cleus. 



Plant cells are equally easy to see. If we 

 peel the skin from one of the fleshy leaves 

 forming an onion bulb, mount it in water to 

 which is added a drop of dilute tincture of 

 iodine, and examine it under a microscope, 

 we find that this skin or epider'mis is also 

 made of cells. Plant cells, however, differ 

 from animal cells in that they have a deli- 

 cate wood wall outside the membrane. 



If we examine the leaves of a green plant 

 we find other structures within the cells. 

 Examination of the delicate leaves of the 

 elo'dea, a water plant used in aquariums, 

 shows a more or less regular arrangement of the cells. But each 

 cell shows many large spaces or vac'uoles, which are filled with a 

 non-living fliiid instead of protoplasm. Forming a part of the 

 protoplasm are many small ovoid bodies, most of which are green 

 in color. These are the chloroplasts (klo'r6-plasts) or chlorophyll 

 (klo'r6-fil) bodies (Gr. chloros, green; phyllon, leaf). We shall 



Profophsm 



Cells of the epidermis of 

 an onion. 



