6 THE VITAL PROCESSES 



tissue, which is everywhere abundant, serves the general 

 purpose of connecting the different parts together. Carti- 

 laginous tissue forms smooth coverings over the ends of 

 the bones and, in addition to this, supplies the necessary 

 stiffness in organs like the larynx and the ear. The 

 nervous tissue controls the body and brings it into proper 

 relations with its surroundings, while the epithelial tissue 

 (found upon the body surfaces and in the glands) supplies 

 it with protective coverings and secretes liquids. The adi- 

 pose tissue (fat) prevents the too rapid escape of heat from 

 the body, supplies it with nourishment in time of need, 

 and forms soft pads for delicate organs like the eyeball. 



Properties of the Tissues. If we inquire how the tissues 

 are able to serve such widely different purposes, we find 

 this answer. The tissues differ from one another both in 

 composition and in structure and, on this account, differ in 

 their properties. 1 Their different properties enable them 

 to serve different purposes in the body. Somewhat as 

 glass is adapted by its transparency, hardness, and tough- 

 ness to the use made of it in windows, the special proper- 

 ties of the tissues adapt them to the kinds of service which 

 they perform. Properties that adapt tissues to their work 

 in the body are called essential properties. The most im- 

 portant of these essential properties are as follows : 



i. Of osseous tissue, hardness, stiffness, and toughness. 

 2. Of muscular tissue, contractility and irritability. 3. Of 

 nervous tissue, irritability and conductivity. 4. Of carti- 

 laginous tissue, stiffness and elasticity. 5. Of connective 

 tissue, toughness and pliability. 6. Of epithelial tissue, 

 ability to resist the action of external forces and power to 

 secrete. 



1 The properties of substances are the qualities or characteristics (color, weight, 

 etc.) by means of which they are recognized. 



