ORGANIZATION. 41 
3. Organs, and their Functions.— Animals, like Plants, 
grow, reproduce, and die: these three are the capital facts 
of every organism. Out of these may issue some peculiar 
phenomena, as Motion and Will. 
Life is manifested in certain special acts, called fune- 
tions, performed by certain special parts, called organs. 
Thus, the stomach is an organ, whose function is digestion. 
A single organ may manifest vitality, but it does not (save 
in the very lowest forms) show forth the whole life of the 
animal. For, in being set apart for a special purpose, an 
organ takes upon itself, so to speak, to do something for 
the benefit of the whole animal, in return for which it is 
absolved from doing many things. The stomach is not 
called upon to circulate or purify the blood. 
There may be functions without organs, as the organless 
Amceba digests, respires, moves, and reproduces by its gen- 
eral mass. But as we ascend the scale of animal life, we 
pass from the simple to the complex: groups of cells or 
tissues, instead of being repetitions of each other, take on 
a difference, and become distinguished as special parts 
with specific duties. The higher the rank of the animal, 
the more numerous the organs. The more complicated 
the structure, the more complicated the functions. But in 
all animals, the functions are performed under conditions 
essentially the same. Thus, respiration in the Sponge, the 
Fish, and in Man has one object and one means, though 
the methods differ. A function, therefore, is a group of 
similar phenomena produced by like causes. 
The life of an animal consists in the accumulation and 
expenditure of force. The tissues are store-houses of pow- 
er, which, as they waste and decay, is given off in various 
forms. Thus, the nervous tissue generates nerve-force ; the 
muscles, motion; and the fatty elements, heat. If we con- 
template the phenomena presented by a Dog, the most 
obvious fact is his power of moving from place to place, 
