accumulated these particles in particular regions. This concentration is effected very slowly, very progressively. In other ulterior droplets, these regions have progressively delimited themselves; later on, the motions of contraction have gradually oriented themselves to one direction rather than another; still later, this habitual direction of alternate contractions and elongations has determined the formation of the contractile substance into fibrillæ arranged in the same direction, and has achieved the formation of muscular fibers; and so on.
Nature, therefore, has not accomplished the formation of differentiated elements at the first stroke. It has created living matter, simple and homogeneous; and this has been called, through a considerable series of ages and generations, to elaborate the differentiated elements with which we are acquainted. More than Nature can do must not be demanded of the chemist. Those who ask him to create directly the cell and muscular fiber infinitely exceed the absurdity of the persons who would tell the miner, whose business is limited to extracting the mineral, to make an iron-clad vessel with his ordinary tools and methods. He could supply the mineral, but a metallurgist would be needed, with furnaces, retorts, and reagents, to extract the crude metal from it. After him would have to come, to conceive and draw the plans, the founder, men to manipulate the rollers and the hammers, the turners, the polishers, the fitters, and the builders proper, all of whom would contribute in succession and through a long series of days to the preparation, the perfection, and the starting of the various parts of the great vessel; and all this under the eye and direction of the engineer who has conceived the plan and ordered the execution of the work, and provided the means of carrying it into effect.
In like manner an innumerable series of minute workers and minute laboratories have contributed, in conformity with the plan of the Creator, to the differentiation of muscular fiber, of the starch-grain, and of the nervous cell.
What can be expected of the chemist is thus well defined and outlined: it is to create simple living matter—albumen or protoplasm—as Nature has created it. We are authorized to believe that he can do this by the progress that has been recently and rapidly made in organic syntheses.
We have remarked, it is true, that, although the synthesis of albumen has been effected, living albumen, active like that of protoplasm, endowed with a strong leavening power and an instability adapted to vital changes, has not been produced. It is not impossible, as Pfluger believes, that non-living and active albumen are isomers—that is, bodies having the same elementary composition, and differing only in the arrangement of the atoms in the molecule.