INTRODUCTION, 
15 
must be so arranged as to render possible the whole living being, not only with regard 
to itself, but to its surrounding relations ; and the analysis of these conditions fre- 
quently conducts to general laws, as demonstrable as those which are derived from 
calculation or experiment. 
It is only w'hen all the laws of general physics, and those which result from the condi- 
tions of existence, are exhausted, that we ^re reduced to the simple laws of observation. 
The most effectual mode of observing is by comparison. This consists in suc- 
cessively studying the same bodies in the different positions in which Nature 
places them, or in a comparison of different bodies together, until constant relations 
are recognized between their structures and the phenomena which they manifest. 
These various bodies are kinds of experiments ready prepared by Nature, who adds 
to or subtracts from each of them different parts, just as we might wish to do in our 
laboratories, and shows us herself the results of such additions or retrenchments. 
It is thus that we succeed in establishing certain laws, which govern these relations, 
and which are employed like those that have been determined by the general sciences. 
The incorporation of these laws of observation with the general laws, either directly 
or by the principle of the conditions of existence, would complete the system of the 
natural sciences, in rendering sensible in all its parts the mutual influence of every 
being. This it is to which the efforts of those who cultivate these sciences should tend. 
All researches of this kind, however, presuppose means of distinguishing with certainty, 
and causing others to distinguish, the objects investigated ; otherwise we should be 
incessantly liable to confound the innumerable beings which Nature presents. Natural 
History, then, should be based on what is called a System of Nature, or a great catalogue, 
in which aU beings bear acknowledged names, may be recognized by distinctive cha- 
racters, and distributed in divisions and subdivisions themselves named and characterized, 
in which they may be found. 
In order that each being may always be recognized in this catalogue, it should carry 
its character along with it: for which reason the characters should not be taken 
from properties, or from habits the exercise of which is transient, but should he 
drawn from the conformation. 
There is scarcely any being which has a simple character, or can be recognized by 
an isolated feature of its conformation : the combination of many such traits is almost 
always necessary to distinguish a being from the neighbouring ones, which have 
some but not all of them, or have them combined with others of which the first is 
destitute ; and the more numerous the beings to be discriminated, the more must 
these traits accumulate : insomuch that, to distinguish from all others an individual 
being, a complete description of it must enter into its character. 
It is to avoid this inconvenience that divisions and subdivisions have been invented. 
A certain number of neighbouring beings only are compared together, and their par- 
ticular characters need only to express their differences, which, by the supposition itself, 
are the less important parts of their conformation. Such a reunion is termed a genus. 
The same inconvenience would recur in distinguishing genera from each other, were 
it not that the operation is repeated in collecting the neighbouring genera, so as to form 
an order ; the neighbouring orders to form a class, &c. Intermediate subdivisions may 
also be established. 
This scaffolding of divisions, the superior of which contain the inferior, is what is 
