12 



HUMAN BIOLOGY 



ends of the muscles are composed almost wholly of it. If 

 every other tissue were removed, the connective tissue 

 would still give a perfect model of all the organs. How 

 abundant this tissue is in the skin may be known from the 

 fact that leather consists entirely of it. 



Fatty (Adipose) Tissue. Fatty tissue is formed by the 

 deposit of oil in connective tissue cells (see Fig. 14). Fat is 



held in meshes of 

 connective tissue 

 fibers. That fatty 

 tissue consists not 

 alone of fat, but of 

 fibers also, is shown 

 when hog fat is 

 rendered into lard, 

 certain tough parts 

 called "crack- 

 lings" being left. 

 What is the differ- 

 ence between beef 

 fat and tallow ? 



Epithelial tissue 

 consists of one or 

 more layers of dis- 

 tinct cells packed 

 close together (see 

 Fig. 15). It con- 

 tains no connective tissue or other fibers, and is the simplest 

 of the tissues. Epithelial tissue forms the outer layer of 

 the skin, called the epidermis, and the mucous membrane 

 lining the interior of the body. It contains no blood ves- 

 sels, the epithelial cells obtaining their nourishment from 

 the watery portion of the blood which soaks through the 



FIG. 14. FATTY TISSUE. Five fat cells, held in 

 bundles of connective tissue fibers. 



is a large oil drop; ;, cell wall; nucleus () and proto- 

 plasm (/) have been pushed aside by oil drop (a). 



