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 Beat ao be ara RTA Sry an Oe 
roducedeinnthis way is\ known aS Guctieed teumens Ge. comective 
forous connective tissue; Lt oe co tiie mae Of white. Shes 
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 
