244 ANIMAL BIOLOGY 



also cross striations running across the cell, and generally 

 several nuclei in each fiber. In unstriated muscle the 

 cells are generally smaller, and have no cross striations and 

 there is one nucleus to a cell. 



Nervous tissue is composed of cells and fibers which make 

 up the nervous system. 



Most organs of the body are composed of several tissues. 

 The heart for instance consists mainly of muscle fibers, 

 but these fibers are held together by connective tissue. 

 There is a coat of epithelium lining the cavity of the heart 

 as well as its outer surface, and there are nerve cells and 

 fibers embedded in the heart muscle. 



