But further: the modern development of biology has emphasised a special problem, which was first formulated by Leibnitz (though it is in antithesis to his fundamental Monad-theory), and which appears incapable of solution on mechanical lines. Leibnitz declared living beings to be “machines,” but machines of a peculiar kind. Even the most complicated machine, in the ordinary sense, consists of a combination of smaller “machines,” that is to say, of wheels, systems of levers, &c., of a simpler kind. And these sub-machines may in their turn consist of still simpler ones, and so on. But ultimately a stage is reached when the component parts are homogeneous, and cannot be analysed into simpler machines. It is otherwise with the organism. According to Leibnitz it consists of machines made up of other machines, and so on, into the infinitely little. However far we can proceed in our analysis of the parts, we shall still find that they are syntheses, made up of most ingeniously complex component parts, and this as far as our powers of seeing and distinguishing will carry us. That is to say: organisation is continued on into the infinitely little.
Leibnitz’s illustration of the fish-pond is well known. He could have no better corroboration of his theory than the results of modern investigation afford. His doctrine of the continuation of organisation downwards into ever smaller expression is confirmed to a certain extent even by anatomy. By analysing structural organisation down to cells a definite point seemed to have been reached. But it now appears that at that point the problem is only beginning. One organisation is made up of other organisations—cells, protoplasm, nucleus, nucleolus, centrosomes, and so on, according to the power of the microscope; and these structures, instead of explaining the vital functions of growth, development, multiplication by division, and the rest, simply repeat them on a smaller scale, and are thus in their turn living units, the aggregation of which is illustrated better by the analogy of a social organism than by that of a mechanical structure.
In order to follow the mechanical explanation along the six lines we have previously indicated, we shall, as we have already said, entrust ourselves to the specialists who are on the opposite side. The difficulties and objections which the mechanical theory has to face have forced themselves insistently upon us even in the course of a short sketch such as has just been given, but they will be clearly realised if we approach them from the other side. But, first of all, a word as to the fundamental and, it is alleged, unassailable doctrine on which the theory as a whole is based, the “law of the conservation of energy.” The appeal to this, at any rate in the way in which it is usually made, is apt to be so distorted that the case must first be clearly stated before we can get further with the discussion.