Limits have been assigned to the duration of all living beings. The same power to whom they owe their creation, their organization, and their endowments, has also subjected them to the inexorable Law of Mortality; and has ordained that the series of actions which characterise the state of life, shall continue for a definite period only, and shall then terminate. The very same causes which, at the earlier stages of their existence, promoted their developement and growth, and which, at a maturer age, sustained the vigour and energies of the system, produce, by their continued and silent operation, gradual changes in the balance of the functions, and, at a later period, effect the slow demolition of the fabric they had raised, and the successive destruction of the faculties they had originally nurtured and upheld. With the germs of life, in all organized structures, are conjoined the seeds of decay and of death; and however great may be the powers of their vitality, we know that those powers are finite, and that a time must come when they will be expended, and when their renewal, in that individual, is no longer possible.

But although the individual perishes, Nature has taken special care that the race shall be constantly preserved, by providing for the production of new individuals, each springing from its predecessor in endless perpetuity.