Page:Life and death (1911).djvu/189

 or the framework of the albuminoid molecule; in other words, its chemical nucleus.

Physical Characters of Protoplasm.—About 1860 Ch. Robin thought that he had defined living matter sufficiently—or, at least, as perfectly as could be expected at that time—by attributing to it three physical characteristics. They were:—Absence of homogeneity, molecular symmetry, and the association of three orders of immediate principles—albuminoids, carbohydrates and fats. These characteristics assist, but do not suffice, to define the organization.

No doubt the characteristics must be completed by the addition of a certain number of more subtle physical features.

One of them refers to the structure of protoplasm as revealed by the microscope. Throughout the whole of the living kingdom, from the bacteria studied by Kunstler and Busquet to the most complicated protozoa, protoplasmic matter presents the same constitution, and in consequence, this structure of the protoplasm must be considered as one of its distinctive characters. It is not homogeneous; it is not the last term of the visible organization: it is itself organized. Experiment shows that it does not resist breaking up or crushing. Mutilations cause it to lose its properties. As for the kind of structure that it presents, it may be expressed by saying that it is that of a foamy emulsion.

We saw above that our knowledge as to the physical condition of protoplasm has been completed by the theories of Bütschli's micellæ or Pfeffer's tagmata.

''Properties of the Protoplasm. Its Affinity for Oxygen.''—From the chemical point of view, living matter presents a very remarkable property—namely,