Connective Tissues. 



25 



substance or matrix. The cellular portion is formative, and is 

 much more conspicuous in the embryonic than in the adult condi- 

 tion. All connective tissues are products of an embryonic tissue, 

 "the mesenchyme (Fig. 23, ms.), which consists of branched cells 

 connected together by their outstanding processes. Through the 

 activity of the cells there is formed an intercellular material con- 

 sisting either of a homogeneous matrix, or more frequently a matrix 

 containing formed elements of a supportive nature. 



A. Ordinary Connective Tissues. 



In the adult condition the ordinary connective tissues, with 

 few exceptions, consist of the cell basis with two kinds of fibrous 

 elements, the white, and yellow 

 fibres (Fig. 6). White fibres are 

 elements of great strength. They 

 are fine, unbranched "fibres, which 

 do not occur independently, but 

 are joined in a parallel fashion 

 with one another, forming in this 

 way fibre bundles of larger or 

 smaller size. The yellow fibres are 

 of greater diameter. They branch 

 and communicate, but are not 

 associated to form bundles. They 

 also differ from white fibres in 

 being - highly elastic. The tissue 

 produced in this way is known as 

 fibrous connective tissue. It 

 occurs in several forms according 



to the relative concentration of the two kinds of fibres or the ad- 

 mixture of other materials. 



The commonest kind of fibrous tissue in the adult is that 

 described as areolar. It is characteristic of the subcutaneous 

 tissue (Fig. 5) which connects the skin with the body; but areolar 

 tissue occurs also in various positions where it has a similar function 

 of joining structures loosely together. Subcutaneous connective 

 tissue is a white material, the peculiar appearance and properties 

 of which are due to the fact that the two kinds of fibrous elements 

 are arranged in a loose felt-like network (Fig. 6). When stretched 



Fig. 6. Areolar connective tissue (sub- 

 cutaneous tissue) of the rabbit; from an- 

 embalmed specimen: c.c, connective 

 tissue cell; w.f,, bundle of white fibres; 

 y.f., yellow elastic fibre. 



