The growth of the primary root is limited; sooner or later adventitious roots develop from the axis above the radicle which they ultimately exceed in growth.
If we meet with phenomena which do not fit easily into this view, we have the alternatives either to modify our assumed laws of motion, or to call to our aid adventitious forces, or to examine whethet the discrepancy can be reconciled by the simpler expedient of a new basis of reference.
Just as each kind of fermentation possesses a definite organized ferment, so many diseases are dependent on the presence of a distinct microbe; and just as the gardener can pick out and grow a given plant or vegetable, so the bacteriologist can (in most cases) eliminate the adventitious and grow the special organism - in other words, can obtain a pure cultivation which has the power of bringing about the special disease.
Thus (e.g.) " natural rights " become rights of which the general observance would be useful apart from the institution of civil government; as distinguished from the no less binding " adventitious rights," the utility of which depends upon this institution.
Adventitious value would therefore seem to have been acquired by the bones of the palate through the fact that so great a master of the art of exposition selected them as fitting examples upon which to exercise his skill.