12 



ADVANCED PHYSIOLOGY 



This study of the parts of live organisms may be carried 

 still further; and just as the stairway, or the elevator, or the 

 windows of a house are not made entirely of wood, or of iron, 

 or of glass, so also the human body is not composed through- 

 out of the same kind of material. The nose, for example, is 

 covered with skin; is lined with a smooth, moist membrane; 

 contains a supporting framework, partly of 

 soft cartilage, partly of bone; blood vessels 

 are present in it; nerves make it sensitive to 

 odors and to touch; hairs are provided for 

 straining the air as one breathes; muscles 

 permit slight movements. Such parts as 

 these composing an organ are commoUy 

 called tissues. A tissue is a single kind of 

 living material with the power of doing a 

 single kind of work. Generally, several dif- 

 ferent kinds of tissue occur in the structure 

 of a single organ. The hand, for example, 

 contains bone tissue, muscle tissue, nerve 

 tissue and blood tissue, besides several 

 other kinds. 



Kinds of Tissues. The following are the 

 most important tissues of the human body. 

 Epithelium, or covering tissue, is a thin 

 layer covering the outer and inner sur- 

 faces of the body and of the different organs ; e. g. the 

 outer layers of the skin and the lining of the mouth and 

 throat. 



Supporting tissues include bone, cartilage and connective 

 tissues. Bone forms the skeleton. Cartilage is found in many 

 different regions of the body. It is placed between each two 

 pieces of the 'back-bone'; it composes the principal part of the 

 voice-box; it makes the ears and the nose somewhat rigid; it 

 covers the ends of bones where they come together at moving 



Tendon 



FIG. 2. THE LEG 



Showing the bones, 

 muscles and tendons 

 concerned in lifting 

 the body upon the 

 toes. 



