But in drawing this conclusion our logic is at fault. The real interpretation suitable to this case, as in all others, is that the specific form is suitable to the substance, and also to the physical, chemical, and mechanical conditions in which it is placed. And the proof is that this same substance, sulphur, which takes the prismatic form immediately after fusion, will not retain that form, but will pass on to the quite different octahedral form. It is so with the specific form of the living being—that is to say, with the assemblage of its constituent materials co-ordinated in a given system—in a word, with its organization. This is suitable to its substance, and to all the material, physical, chemical, and mechanical conditions in which it is placed. This form is the condition of material equilibrium corresponding to a very complex situation, to a sum of given conditions. The chemical condition is only one of these. And further, it is hardly proper to speak of a “chemical substance” when we refer to an astonishingly complex mixture which is in addition variable from one point to the other of the living body. When we thus reduce phenomena to their original signification, false analogies disappear. To say with Le Dantec that the form of the greyhound is the condition of equilibrium of the “greyhound chemical substance” is saying much; and too much, if it means that the body of the greyhound has a substance which behaves in the same way as homogeneous, isotropic masses like melted sulphur and dissolved salt. It were better to say much less, if it means, as it will in the minds of the physiologists, that the body of the greyhound is the condition of equilibrium of a heterogeneous, anisotropic, material system, subjected to an infinite number of physical and chemical conditions. The idea of connecting form, and by that we mean organization, with chemical composition did not arise in the minds of chemists or physiologists. Both have expressed themselves very clearly on this point. “We must distinguish,” said Berthelot, “between the formation of the chemical substances, the assemblage of which constitutes organized beings, and the formation of the organs themselves. This last problem does not come into the domain of chemistry. No chemist will ever claim to have formed in his laboratory a leaf, a fruit, a muscle, or an organ.... But chemistry has a right to claim that it forms direct principles—that is to say, the chemical materials which constitute the organs.” And Claude Bernard in the same way writes:—“In a word, the chemist in his laboratory, and the living organism in its apparatus, work in the same way, but each with its own tools. The chemist can make the products of the living being, but he will never make the tools, because they are the result of organic morphology.” § 2. THE ACQUISITION AND RE-ESTABLISHMENT OF THE SPECIFIC FORM.