CHAPTER VII 

 THE SUPPORTING AND CONNECTIVE TISSUES 



PROTOPLASM as such has not sufficient tensile strength or rigidity 

 to enable the multicellular body to preserve its proper form. A certain 

 type of cells is found which are devoted to this function. They fulfill 

 it by the formation of fibers, plates, and masses of material, either on the 

 surface of their cytoplasm or within it. These extra-cellular fibers, 

 plates, and masses are made sufficiently strong, rigid, or elastic to meet 

 the requirements for supporting that portion of the body in which they 

 are placed. They are controlled absolutely in their development, 

 growth, and change by the cells from whose cytoplasm they originate. 

 We may call them the cell organs of support or, collectively with the 

 cells that made them, the connective tissues. 



The resistance afforded by the connective tissues to the body is of 

 two kinds : A binding or connecting power secured by thin, strong fibrils 

 in larger or smaller bundles, and a resistance to impact, shearing, or 

 bending pressures met by rigid masses, shells, or rods. We can distin- 

 guish in consequence two classes of these tissues : The tensile or bind- 

 ing and the rigid or supporting connective tissues. It can be seen that 

 all rigid connective tissues have some tensile strength and vice versa, but 

 yet the predominant character of the tissue can be easily determined. 

 In some tissues the two kinds are mixed to meet peculiar conditions. 



Of each of these tissues there are two kinds. In one case the cell 

 organ of support is an intra-cellular organ and is formed inside the cell. 

 This more primitive method is rare and only occurs among the lower 

 forms of life. In the second case the cell- organ is formed outside of 

 the cell, and the same organ (fibril, plate, or mass) is usually formed by 

 several cells jointly. 



Among the vertebrate animals the chemical constitution of the extra- 

 cellular connective material is used to classify the tissues into several 

 groups. As this classification breaks down when extended into the in- 

 vertebrate phyla, we shall not use it. For this classification the reader is 

 referred to some good medical histology. 



Adaptability and extreme range of variation are characteristics of the 

 connective tissues, which develop or change to meet all kinds of require- 

 ments in the growth, renewal, and regeneration of the organism. These 



56 



