24 DISTINCTIVE CHARACTERS OP ANIMALS. 
and excretion, of the effete matters with which the blood be¬ 
comes charged by the decomposition continually going on in 
the body; the maintenance of animal-heat by the same process; 
and the act of reproduction, whereby the race is perpetuated, 
in spite of the limited duration of the individual. The fore- 
. going, which are for the most part common to the Animal and 
the Plant, are termed Organic Functions , or Functions of 
Vegetative Life. But, in addition to these, it is the character¬ 
istic of Animals generally, that they are sensible to impressions 
made by surrounding objects, so that they possess some con¬ 
sciousness of what is going on about them; and that they also 
possess the power of re-acting on those objects by movements 
of their own, so as to change either their own places, or 
the places of surrounding objects in relation to them¬ 
selves. These two functions, sensibility and the power of 
spontaneous motion, being peculiar to animals, are distin¬ 
guished as Animal Functions, or Functions of Animal Life. In 
the higher animals, they are the most important and charac¬ 
teristic phenomena of their existence; so that it would seem 
as if the whole assemblage of organic functions had no other 
destination in them, than to build up and keep in order the 
apparatus by which the functions of animal life are performed. 
But this state of things is entirely reversed among those 
• lower tribes of animals which border most closely on the 
Vegetable kingdom ; for we find that among such, the mani¬ 
festations of sensibility and power of spontaneous movement 
are so feeble, that it may be doubted whether these attributes 
are really present in them ; and even in higher orders, there 
are many in which the proper animal powers are in such a 
low grade of development, that they appear as if they were 
destined merely to minister to the organic functions. 
7. Thus, although the characteristic difference between the 
Animal and the Vegetable kingdom, taking each as a whole, 
may be truly said to consist in the possession by the former 
of endowments which do not exist in the latter, this does not 
express the essential difference between Animals and Plants ; 
since, while there are many tribes among the former in which 
the proper animal powers are reduced to so low a degree as 
to prevent it from being certainly affirmed that they are 
present at all, there are many tribes among the lower plants 
which exhibit a power of spontaneous movement fully as 
