s,
spring motors, weight motors, current motors fluid pressure motors, etc.
A genus is more extensive than any of its species but less intensive.

A "species" is any class that is regarded as forming a part of the next
larger class, "electric motors" being a species of "motors" and "motors"
being a species of "energy transformers." A species is more intensive
than the genus to which it belongs but less extensive.

Every species may be a genus to another species until no further
subdivisions can be made. This last indivisible species is termed the
_infima species_. Every genus may be a species to another genus until a
point is reached where no further generalization may be made or the
_summum genus_ is attained. In the Patent Office classification of the
useful arts, the _summum genus_ is useful arts. The _summum genus_ of
the plastic arts would be plastics. The _infima species_ in the useful
arts evidently never can be attained.

"Proximate species" and "proximate genus" indicate, respectively, those
species that are divided from a genus without intermediate genera, and
those genera from which the species are directly divided. Motors, and
not energy transformers, is the proximate genus to the species, fluid
motors, electric motors, etc., while fluid motors, electric motors,
etc., and not steam engines, alternating current motors, etc., are
proximate species to motors.

[10] In the Manual of Classification of the U. S. Patent Office the
arrangement of subclasses has always been alphabetical, although in the
Supplement containing definitions of revised classes the arrangement is
numerical. If the latter schedule of "Balls" in the text had been
printed in alphabetical order, it is apparent that the species
"Aluminum" and "Zinc" of the genus Metal would be as widely separated as
possible. In the former schedule of "Balls," in which the genus Metal is
printed, "Aluminum" and "Zinc" come together. It is apparent that in an
alphabetical arrangement allied species can not be kept together without
printing every proximate genus. This fact, among others, indicates the
advisability of abandoning the alphabetical arrangement in the
classification manual and adopting the idea arrangement in the schedules
of revised classes, supplemented by a consolidated alphabetical index of
all subclasses.

[11] A species contains all the qualities of the genus and more. These
additional qualities form the "difference." The electric motor has