3. There is not much difficulty in thus forming adjectives: but the purposes of Natural History require that we should have substantives corresponding to these adjectives; and these cannot be obtained without some extension of the analogies of our language. We cannot in general use adjectives or participles as singular substantives. _The happy_ or _the doomed_ would, according to good English usage, signify those who are happy and those who are doomed in the plural. Hence we could not speak of a particular scaled animal as _the squamate_, and still less could we call any such animal _a squamate_, or speak of _squamates_ in the plural. Some of the forms of our adjectives, however, do admit of this substantive use. Thus we talk of _Europeans_, _plebeians_, _republicans_; of _divines_ and _masculines_; of the _ultramontanes_; of _mordants_ and _brilliants_; of _abstergents_ and _emollients_; of _mercenaries_ and _tributaries_; of _animals_, _mammals_, and _officials_; of _dissuasives_ and _motives_. We cannot generally use in this way adjectives in _ous_, nor in _ate_ (though _reprobates_ is an exception), nor English participles, nor adjectives in which there is no termination imitating the Latin, as _happy_, _good_. Hence, if we have, for purposes of science, to convert adjectives into substantives, we ought to follow the form of examples like these, in which it has already appeared in fact, that such usage, though an innovation at first, may ultimately become a received part of the language.