FIBROUS TISSUE. 
123 
When a vertical section of a tendon of any large 
animal is examined, it always presents a silvery lustre, 
and the fibres, collected in bundles, proceed in parallel 
lines, each fasciculus being connected with its neighbour 
by areolar tissue. If a portion of tendon be dried, the 
greater part of the silvery lustre disappears, but when 
viewed by polarised light, not only is the direction of 
the bundles seen, but each displays a series of brilliant 
colours. 
In the human body we have other structures besides 
tendons, which are composed almost entirely of white 
fibrous tissue ; such are the periosteum, dura mater, 
&c. A peculiar form of fibrous tissue occurs in the 
membrana putaminis or membrane lining the interior 
of the shell of the egg of most birds and reptiles ; it 
consists of several layers of fibres of nearly uniform 
diameter, which interlace with each other and produce a 
series of spaces or cells sufficiently large for gases to 
pass through. The fibres in an egg of the common 
Fowl are on an average ^ of an inch in diameter, and 
are not acted on by acetic acid. A thin layer of this 
membrane, having the fibres separated from each other, 
very much resembles the section of Boletus igniarius , 
represented in Fig. 18 . 
