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-muscular 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. For 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. 

 Now 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 (VEGET. 

 PHYS. Chap, in.), becoming mere 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 Animals, as will hereafter appear, they are the im- 

 mediate instruments of the most important among the organic 

 functions, just as they are in Plants. 



