FIBROUS MEMBRANES AND LIGAMENTS. 
41 
strain has to be borne. This is the case with the Ligaments, 
which bind together the bones at the joints, the Tendons , by 
which the muscles are usually attached to the bones, and the 
tough Fibrous Membranes that envelope and protect many 
of the most important viscera. In these any considerable 
amount of elasticity would be misplaced; and we conse¬ 
quently find that they are chiefly or entirely composed of the 
white fibrous tissue. Whenever an elastic ligament is re¬ 
quired, however, we find the white replaced by yellow. One 
of the best examples of this is seen in the ligament of the 
neck of many quadrupeds, commonly known as the paxy- 
waxy; which is given to the large herbivorous quadrupeds, 
such as the ox, to assist them in supporting their heavy 
heads with as little exertion as possible ; whilst carnivorous 
quadrupeds, such as the lion and tiger, are endowed with it 
to give them additional power of carrying away heavy bur¬ 
dens in their mouths. In Man we scarcely find a trace of 
it. This yellow fibrous tissue is found, moreover, in the walls 
of the arteries (§ 248), to which it gives their peculiar elas¬ 
ticity; and it also forms the vocal cords of the larynx (§ 681). 
It is by the same kind of elastic ligament that the claws of 
the Feline tribe are drawn back into their sheaths when not 
in use, being projected (when required) by muscular action; 
and that the two pieces of the shell of Bivalve Mollusks are 
united at the hinge, and are at the same time kept apart for 
the admission of water between them, except when, the 
animal forcibly draws them together by its adductor muscle 
(§ H3). 
30. All these fibrous tissues, then, are concerned in actions 
purely mechanical; and there is nothing in their properties 
which is so distinct from those of inorganic substances, as to 
require to be considered as vital. We may consider them, 
therefore, as among the lowest forms of animal tissue; and 
accordingly we find that, when the higher forms degenerate 
or waste away, these appear in their place. Such a degene¬ 
ration may take place simply from want of use. Thus if, 
from palsy or want of power of the nerves, the muscles of 
the legs are disused for several years, they will lose their 
peculiar property of contractility (§ 5 ); and it will be found 
that scarcely any true muscular structure remains, but that it 
is replaced by some form of fibrous tissue. Or again, if the 
