THE SUPPORTING TISSUES 41 



make the whole bone strong and rigid. Thus the hard, min- 

 eral part of the bone is deposited by these bone cells and is 

 nourished by them. The bone corpuscles, we thus see, lie 

 in the intercellular substance or matrix, in much the same 

 way that the cartilage cells lie in the intercellular substance 

 of the cartilage. In bone the matrix consists mostly of lime. 



67. Aided by the figures, make a series of drawings 

 showing the form of the cell in the several tissues. Can 

 you see that the cell has not only similar parts but also 

 similar functions, in each of the tissues studied ? Some 

 cells live only a few hours ; others, as the cells of cartilage 

 and bone, may live for years. 



68. It should be repeated that each organ of the body 

 consists not of one, but of several tissues. The heart, for 

 example, is composed principally of muscular, nervous, con- 

 nective, and fatty tissues ; the eye is formed of nervous, 

 connective, muscular, and epithelial tissues. The following 

 list shows the several classes of tissues : 



MASTER TISSUES ( N;ous Tissues 

 [ Muscular Tissues 



( Connective Tissues 



Fatty Tissues 

 SUPPORTING TISSUES J Cartilaginous Tissues 



Osseous Tissues 

 ^ Epithelial Tissues 



69. Tissue Building. As you have learned, all of the 

 tissues are built, maintained, and repaired by living cells. 

 Life and health depend upon the proper and continuous 

 activity of these cells, and anything which aids in this 

 activity strengthens the body and prolongs life; any- 

 thing which injures them or interferes with their activity, 

 impairs the health and shortens life. Growth and repair 

 of tissue are promoted by sunshine, by fresh air, by drinking 

 plenty of pure water, by good food, by active and happy 

 occupation. Weakness and injury of cell and tissue 



