Sin,—Surely Professor Metchnikoff's predictions are worthy of something more than
criticism by acetic acid and scepticism. It is now quite a considerable time since science has settled that the nature of life is, for every vital function, a ferment. That is to say that the brain, lungs, and so on each have their special ferment to make them what they are. Nor is this all. Croft Hill has dis- covered, and Emmerling has verified, that ferments are
reversible ; that is, may be constructive as well as destructive. True, the actual life ferments have not yet been found; but Bredig and others have imitated the ferment actions of life very closely, and have actually produced enzymes not normal in the organism. No doubt it is a far cry even from pro- ducing artificial parthenogenesis—i.e., producing life from unfertilised eggs—as Loeb has done, to arresting old age or creating a live man. But for all that, the theory that all processes of life are reversible, that an oak may be turned back into an acorn, or a grown man into a child, rests upon much more than mere hypothesis. What would happen if—dare I say ?—eternal life were discovered, on which you wrote an interesting article ? Is not religion mainly a medita- tion on death ? And if death were not, who would meditate thereon P Would not such a discovery also affect the entire social polity ? Could younger sons submit to being younger for ever ? Could Governments which still retain capital punishment allow the executed criminal to be restored to earth again, or would they have to monopolise the life dis- covery under given pledge not to utilise it in their own favour, or in that of the Opposition ? Amongst the many scientific books which deal with the subject of life ferments, Carl Snyder's "New Conceptions in Science" may be mentioned as one easy to be understood by the vulgar.—I am, Sir, &c., Downcliffe, Filey. ALFRED J. BETHELL.