CONNECTIVE TISSUE 



41 



squamous form, while a section of the intestine Uning (see 

 Ex. XXV.) illustrates the columnar or cylindrical forms. 

 Sometimes the cells are modified in various ways. For 

 example, in the skin, hair, and teeth the external cells 

 become hard or horny, while the cells that line the breath- 

 ing passages may develop hairlike projections of proto- 

 plasm called cilia. These cilia wave back and forth and 

 thus free the surface of tiny particles of dust, etc. In 

 secretory epithelium the secreting cells are often goblet 

 shaped. 



Connective tissue. — If we attempt to pull apart a piece 

 of beef we find that it resists 

 this action by means of an in- 

 tricate interlacing of white fibers 

 that hold the separate parts 

 together. These fibers make 

 up what is called intermuscular 

 tissue, which, in turn, is a form 

 of connective tissue. These 

 fibers are not cells, but are 

 formed in the matter thrown 

 off by certain cells. They are 

 of two kinds, white inelastic, and 

 yellow elastic, fibers, and their 

 function is to surround and 

 connect other layers. Hence 

 the name, connective. It is evi- 

 dent then that the connecting 



is done by the substance given off by cells and not by cells 

 themselves. This characteristic holds true of all forms of 

 connective tissue. The cells are small and of importance 

 only as makers of the connective part which is called inter- 



Oorpuscle 



Bundle of White Fibers 



Fig. 12 — Intermuscular connect- 

 ive tissue. Corpuscles are the 

 cells which form the fibers. 



