Further, in the _elementary life_ peculiar to monocellular beings (protozoa and cellular elements), M. Le Dantec distinguishes three manners of being:—The first condition, which is elementary life manifested in all its perfection, cellular health; the second condition is deteriorated elementary life, _cellular disease_; and the third condition, which is _latent life_. I should say at once that in so far as the fundamental distinction of the phenomena of _elementary life_ and those of the general life of animals and ordinary plants, metazoa or metaphytes is concerned, we find it neither justified nor useful. And further, _manifested elementary life_, as M. Le Dantec understands it, would only belong to a small number of _elementary beings_—for the protozoa, starting with the infusoria, are not among the number—and to a still smaller number of _anatomical elements_, since among the vertebrates we recognize as almost the only elements satisfying it, the ovule, and perhaps the leucocyte. Physiologists, therefore, do not agree with M. Le Dantec as to the utility of adding one condition more to those we all admit—namely, manifested animal life and latent life. _The Doctrine of the Vital Duality of Animals and Plants._—There are, therefore, biologists who, in the domain of theory and in virtue of more or less well-founded conceptions or interpretations, separate _elementary life_ from other vital forms, and thus break the bond of vital unity proclaimed by Claude Bernard. This monistic doctrine at the outset met with other opponents, and that, too, in the domain of facts. But it triumphed over them and became established. We have to deal with scientists like J. B. Dumas and Boussingault, who drew a dividing line between _animal life_ and _vegetable life_.