definition only of the very lowest species, as of a Fungus or a Mollusca; and just as comprehensive an idea of the mystery of Life, as a Mollusca might give, can this definition afford. But this is not the only objection. For, _first_, it is not pretended that we begin with seeking for an organ evidently appropriated to nutrition, and then infer that the substance in which such an organ is found _lives_. On the contrary, in a number of cases among the obscurer animals and vegetables we infer the organ from the pre-established fact of its life. _Secondly_, it identifies the process itself with a certain range of its forms, those, namely, by which it is manifested in animals and vegetables. For this, too, no less than the former, presupposes the arbitrary division of all things into not living and lifeless, on which, as I before observed, all these definitions are grounded. But it is sorry logic to take the proof of an affirmative in one thing as the proof of the negative in another. All animals that have lungs breathe, but it would be a childish oversight to deduce the converse, viz. all animals that breathe have lungs. The theory in which the French chemists organized the discoveries of Black, Cavendish, Priestly, Scheele, and other English and German philosophers, is still, indeed, the reigning theory, but rather, it should seem, from the absence of a rival sufficiently popular to fill the throne in its stead, than from the continuance of an implicit belief in its own stability. We no longer at least cherish that intensity of faith which, before Davy commenced his brilliant career, had not only identified it with chemistry itself, but had substituted its nomenclature, even in common conversation, for the far more philosophic language which the human race had abstracted from the laboratory of Nature. I may venture to prophecy that no future Beddoes will make it the corival of the mathematical sciences in demonstrative evidence. I think it a matter of doubt whether, during the period of its supposed infallibility, physiology derived more benefit from the extension, or injury from the misdirection, of its views. Enough of the latter is fresh in recollection to make it but an equivocal compliment to a physiological position, that it must stand or fall with the corpuscular philosophy, as modified by the French theory of chemistry. Yet should it happen (and the event is not impossible, nor the supposition altogether absurd,) that more and more decisive facts should present themselves in confirmation of the metamorphosis of elements, the position that life consists in assimilation would either cease to be distinctive, or fall back into the former class as an identical proposition, namely, that Life, meaning by the word that sort of growth which takes place by means of a peculiar organization, consists in that sort of growth which is peculiar to organized life. _Thirdly_, the definition involves a still more