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GENERAL STRUCTURE Qt\JHE BODY. 15 



TRAINING SCHC 



being filled with the material the gland secretes. Finally, 

 ciliated epithelium is composed cH^columnar cells with 

 cilia or little hair-like processes upo 

 which serve to send secreted fluids and other matters 

 along the surfaces where they occur, as in the air pas- 

 sages, parts of the generative organs, the ventricles of 

 the brain, and the central canal of the spinal cord. 



Connective tissue has a great deal of intercellular sub- 

 stance. One form, areolar tissue, is composed of a loose 

 network of fine white fibers with a few yellow elastic 

 fibers interspersed and with cells lying in the spaces 



Pavement cell. 

 Pear-shaped cell. 



Interstitial cell. 



FIG. 2. Section of bladder epithelium. (Hill.) 



between the fibers. It connects and surrounds the differ- 

 ent organs and parts, holding them together, yet allowing 

 free motion, and is one of the most extensively distrib- 

 uted of the tissues. It is continuous throughout. 



Closely allied to the areolar is the fibrous tissue, in 

 which the white fibers lie close together and run for the 

 most part in one direction only. This is found in liga- 

 ments, joints and tendons, as also in such fibrous pro- 

 tective membranes as the periosteum, dura mater, the 

 fascia of muscles, etc. Fibrous tissue is silvery white in 

 appearance and is very strong and tough, yet pliant. 

 It is not extensile. 



Elastic tissue, on the other hand, has a large predomi- 

 nance of yellow elastic fibers and is very extensile and 

 elastic, though not so strong as the fibrous. It is found 

 in the walls of the blood-vessels, especially the arteries, 



