30 
DISTINCTIVE CHARACTERS OF ANIMALS. 
many which, are fixed to one spot during nearly their whole 
lives, and which grow and extend themselves like plants, the 
movements of the body are but few in number, and trifling 
as to their variety; these movements are only destined to 
assist in the performance of the organic functions, as by 
bringing food to the mouth, and water to the respiratory 
organs; and the nervo-muscuiar apparatus by which they 
are effected, bears so small a proportion to the organs of 
nutrition, as to seem like a mere appendage to them, and is 
sometimes altogether undiscoverable. This is the case, for 
example, in the lowest kinds of shell-fish, such as the Oyster, 
and in the Coral-polypes. 
12. Hence we perceive, as we descend the Animal scale, a 
nearer and nearer approach to the character of Plants; and 
this we shall find to be the case, not only in the general 
arrangement of the organs, but also in the nature of the 
elementary tissues of which these are composed. Por in the 
higher animals, the whole organism is constructed in such a 
manner as to admit a free motion in its individual parts. 
The different portions of the skeleton or hard framework are 
connected with each other by flexible ligaments, which are 
adapted to resist a very powerful strain; the muscles are 
attached to these by fibrous cords or tendons, which, also, 
can support a vast weight ; and the several muscles and 
other parts, which need to be mutually connected, but also 
require a certain power of moving independently of one 
another, are bound together by a very elastic loosely-arranged 
tissue, consisting of fibres crossing and interlacing in every 
direction, the interstices between which are filled with fluid. 
How to these fibrous tissues, there is nothing analogous in 
plants, because no freedom of motion is required, or even 
permitted, among their parts ; and we find them bearing a 
less and less proportion to the whole, as we descend the 
animal scale. On the other hand, we find the various forms 
of true cellular tissue, such as predominate in plants (V eget. 
Phys. Chap, hi.), becoming more and more abundant, as we 
pass from the highest to the lowest animals, and having 
more and more important duties to fulfil. But even in the 
highest Ani mals, as will hereafter appear, they are the im¬ 
mediate instruments of the most important among the organic 
functions, just as they are in Plants. 
