“Enfin, une loi sans exception me semble apparaitre dans les faits nombreux que j’ai observes et conduire a envisager sous un nouveau jour la vie vegetale; si je ne m’abuse, tout ce que dans les tissus vegetaux la vue directe ou amplifiee nous permet de discerner sous la forme de cellules et de vaisseaux, ne represente autre chose que les enveloppes protectrices, les reservoirs et les conduits, a l’aide desquels les corps animes qui les secretent et les faconnent, se logent, puisent et charrient leurs aliments, deposent et isolent les matieres excretees.”

And again:—­

“Afin de completer aujourd’hui l’enonce du fait general, je rappellerai que les corps, doue des fonctions accomplies dans les tissus des plantes, sont formes des elements qui constituent, en proportion peu variable, les organismes animaux; qu’ainsi l’on est conduit a reconnaitre une immense unite de composition elementaire dans tous les corps vivants de la nature."[7]

[Footnote 7:  Mem. sur les Developpements des Vegetaux, &c.—­Mem.  Presentees. ix. 1846.]

In the year (1846) in which these remarkable passages were published, the eminent German botanist, Von Mohl invented the word “protoplasm,” as a name for one portion of those nitrogenous contents of the cells of living plants, the close chemical resemblance of which to the essential constituents of living animals is so strongly indicated by Payen.  And through the twenty-five years that have passed, since the matter of life was first called protoplasm, a host of investigators, among whom Cohn, Max Schulze, and Kuehne must be named as leaders, have accumulated evidence, morphological, physiological, and chemical, in favour of that “immense unite de composition elementaire dans tous les corps vivants de la nature,” into which Payen had, so early, a clear insight.

As far back as 1850, Cohn wrote, apparently without any knowledge of what Payen had said before him:—­

“The protoplasm of the botanist, and the contractile substance and sarcode of the zoologist, must be, if not identical, yet in a high degree analogous substances.  Hence, from this point of view, the difference between animals and plants consists in this; that, in the latter, the contractile substance, as a primordial utricle, is enclosed within an inert cellulose membrane, which permits it only to exhibit an internal motion, expressed by the phenomena of rotation and circulation, while, in the former, it is not so enclosed.  The protoplasm in the form of the primordial utricle is, as it were, the animal element in the plant, but which is imprisoned, and only becomes free in the animal; or, to strip off the metaphor which obscures simple thought, the energy of organic vitality which is manifested in movement is especially exhibited by a nitrogenous contractile substance, which in plants is limited and fettered by an inert membrane, in animals not so."[8]

[Footnote 8:  Cohn, “Ueber Protococcus pluvialis,” in the Nova Acta for 1850.]