ls into
vertebrate and not vertebrate. By continuing the process of division in
the same manner, the division is obviously exhaustive of the subject,
there being always a negative subdivision to receive any subsequently
created or discovered species. Although bifurcate division has been
ridiculed by some, it is agreed by highest authority that it is the only
plan of division by which one can be sure to have a consistent place for
everything, or by which one can be certain that the divisions are
mutually exclusive. It can be demonstrated that a classification
schedule in which the relation of genera and species is shown by
indentions, if correctly formed on the principles now sought to be
applied in the revision of the Patent Office classification, is
susceptible of conversion into a tree of Porphyry, while unlike the
latter it is compact and wieldy.

_Utility of arrangement according to resemblances._--The expedient of
indicating kinds of relationship between several equally indented
divisions by relative position has the following utility:

(1) A uniform rule is provided, applicable to all classes, for placing
inventions that bear the relation of whole to part in subdivisions
before those that bear the relation of a part to that whole, and those
that are defined by a particular effect, product, material, or use
before those that are defined by a function or an operation applicable
generally to various effects, products, materials, or uses; whereby that
portion of the schedule in which any invention belonging to any
particular class should be found may be approached whether or not the
investigator knows the name of the object sought for or the title of the
appropriate subdivision.

(2) The substantial impossibility of dividing many branches of the
useful arts exhaustively into a reasonable number of mutually exclusive
or non-overlapping subclasses is compensated for; so that when the
classifier or the searcher has an invention to place or to find
including two or more different kinds of characteristics, for each of
which a subdivision is provided, but no subdivision for the plural
characteristics, it will be known that the invention should be in the
subclass for that characteristic which stands before the subclass for
the other characteristic.

(3) It compensates for omission of some generic titles that if written
in the indented schedule would lengthen specific titles to a cumbersome
extent.

(4) It provides a r