ANIMAL PHYSIOLOGY. 
GENERAL BIOLOGY. 
INTRODUCTION. 
BIoLoGYy (ws, life; Aoyos, a dissertation) is the science 
which treats of the nature of living things; and, since the 
properties of plants and animals can not be explained without 
some knowledge of their form, this science includes morphol- 
ogy (vopdy, form; Aoyos, a dissertation) as well as physiology 
(pvors, nature ; Acyos). 
Morphology describes the various forms of living things 
and their parts; physiology, their action or function. 
General biology treats neither of animals nor plants exclu- 
sively. Its province is neither zodlogy nor botany; but it at- 
tempts to define what is common to all living things. Its aim 
is to determine the properties of organic beings as such, rather 
than to classify or to give an exhaustive account of either ani- 
mals or plants. Manifestly, before this can be done, living 
things, both animal and vegetable, must be carefully compared, 
otherwise it would be impossible to recognize differences and 
resemblances; in other words, to ascertain what they have in 
common. 
When only the highest animals and plants are contem- 
plated, the differences between them seem so vast that they 
appear to have, at first sight, nothing in common but that they 
are living: between a tree and a dog an infant can discrimi- 
nate; but there are microscopic forms of life that thus far 
defy the most learned to say whether they belong to the ani- 
mal or the vegetable world. As we descend in the organic 
series, the lines of distinction grow fainter, till they seem 
finally to all but disappear. 
But let us first inquire: What are the determining charac- 
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