But although Bathybias proved delusive, this did not materially affect the advance and development of the doctrine of protoplasm.  Simple forms of protoplasm were found, although none quite so simple as the hypothetical Bathybias.  The universal presence of protoplasm in the living parts of all animals and plants and its manifest activities completely demonstrated that it was the only living substance, and as the result of a few years of experiment and thought the biologist’s conception of life crystallized into something like this:  Living organisms are made of cells, but these cells are simply minute independent bits of protoplasm.  They may contain a nucleus or they may not, but the essence of the cell is the protoplasm, this alone having the fundamental activities of life.  These bits of living matter aggregate themselves together into groups to form colonies.  Such colonies are animals or plants.  The cells divide the work of the colony among themselves, each cell adopting a form best adapted for the special work it has to do.  The animal or plant is thus simply an aggregate of cells, and its activities are the sum of the activities of its separate cells; just as the activities of a city are the sum of the activities of its individual inhabitants.  The bit of protoplasm was the unit, and this was a chemical compound or a simple mixture of compounds to whose combined physical properties we have given the name vitality.

==The Decline of the Reign of Protoplasm.==—­Hardly had this extreme chemical theory of life been clearly conceived before accumulating facts began to show that it is untenable and that it must at least be vastly modified before it can be received.  The foundation of the chemical theory of life was the conception that protoplasm is a definite though complex chemical compound.  But after a few years’ study it appeared that such a conception of protoplasm was incorrect.  It had long been suspected that protoplasm was more complex than was at first thought.  It was not even at the outset found to be perfectly homogeneous, but was seen to contain minute granules, together with bodies of larger size.  Although these bodies were seen they were regarded as accidental or secondary, and were not thought of as forming any serious objection to the conception of protoplasm as a definite chemical compound.  But modern opticians improved their microscopes, and microscopists greatly improved their methods.  With the new microscopes and new methods there began to appear, about twenty years ago, new revelations in regard to this protoplasm.  Its lack of homogeneity became more evident, until there has finally been disclosed to us the significant fact that protoplasm is to be regarded as a substance not only of chemical but also of high mechanical complexity.  The idea of this material as a simple homogeneous compound or as a mixture of such compounds is absolutely fallacious.  Protoplasm is to-day known to be made up of parts harmoniously adapted to each other in such a way as to form an extraordinarily intricate machine; and the microscopist of to-day recognizes clearly that the activities of this material must be regarded as the result of the machinery which makes up protoplasm rather than as the simple result of its chemical composition.  Protoplasm is a machine and not a chemical compound.