When, I say, that life consists in motion, I make no assertion derogatory to the Deity, for every philosopher is of opinion that motion is to us as mysterious as life; and when I endeavour to trace in its phenomena a correspondence with physical laws, I conceive that I pay the truest homage to a Deity. At all events, it would be dishonest of me to give my sanction to opinions respecting a difference which seems to me not to subsist. The same causes which terminate motion terminate life. Life begins by motion, and terminates when it ceases; but very curiously it also terminates in consequence of it. In other words, the motion wears out the machine in which it takes place. For, while the functions are most dependent, life encreases; and their very independence, though, to a certain extent, the grand aim of existence, destroys it. The very cause of decay commencing when the different functions have acquired their greatest vigour, arises precisely from their having acquired that vigour, and being, at that moment, most capable of a species of warfare, if I may so term it, with each other, as well, as in some measure, from the greater number of accidents to which a complexity of functions is liable. That, at this period, the functions may, in a certain sense, be said to combat each other, will be evident to every one who, for a moment, considers that great exercise of the loco-motive functions uniformly interrupts the vital and intellectual, or of the vital functions injures the loco-motive and intellectual, or of the intellectual functions injures the loco-motive and vital. These powers are always in an inverse relation to each other. Grimaud seems to have had some idea of this, with regard to the first and second classes of functions. He, says Richerand, has given the most extensive developement to the idea of the constant opposition between those two series of actions, over which preside, according to the opinion of this physician, two powers, which he calls loco-motive and digestive. It is marked in no species of animals more than in the carnivorous, which connect with senses abounding in stratagem, and muscles capable of extraordinary action, an assimilating power of so low a degree, that their aliment, in order to be conveniently digested, must posses a composition analogous to that of their organs. Thus, the independence which the functions acquire, and the interruptions which their operations present to each other, subjects them to the common laws of impeded motion, and its result, a separation of parts. When, in manhood, their unison is most complete, life is most vigorous. When, in old age, this unison ceases, life disappears. Hence also, I am convinced, it is, that those animals whose functions are longest dependent on each other, and who remain longest helpless, longest enjoy organic existence.