Characters of Generation in the Living Being.—Growth of the living substance, and consequently of the being itself, is the fundamental law of vitality. Generation is the necessary consequence of growth (p. 210).
Living elements or cells cannot subsist indefinitely without increasing and multiplying. The time must come when the cell divides, either directly or indirectly; and then, instead of one cell, there are two. This is the method of generation for the anatomical element. In a complex individual it is a more or less restricted part of the organism, usually a simple sexual cell, that takes on the formation of the new being, and assures the perpetuity of the protoplasm, and therefore of the species.
Property of Growth. Its Supposed Restriction to Living Beings.—At first it would appear that nothing like this occurs in inanimate nature. The physical machine, if we furnish it matter and energy, could go on working indefinitely, without being compelled to increase and reproduce. Here, then, there is an entirely new condition peculiar to the organized being, a property well adapted, it would seem—and this time without any possible doubt—for separating living matter from brute matter. It is not so.
It would not be impossible to imagine a system of chemical bodies organized like the animal or vegetable economy, so that a destruction would be compensated for by a growth. The only thing impossible is to suppose, with M. le Dantec, a destruction that would at the same time be an analysis. And an additional perplexity occurs when he supposes that in the successive acts exchanges of material may occur.
There is no necessity for making this impossible chemistry a characteristic of the living being. The chemistry of the living being is general chemistry. Lavoisier and Berthelot enforced this view. We should not lose sight of the teachings of the masters.
Let us return to generation, properly so called, and find in it the characteristics of brute bodies and of crystals.
The Sowing of Micro-organisms.—When a microbiologist wishes to propagate a species of micro-organisms, he places in a culture medium a few individuals (one is all that is actually necessary), and soon observes their rapid multiplication. Usually, if only the ordinary microbes in atmospheric dust are wanted, the operator need not trouble to charge the culture; if the culture tube remains open and the medium is suitably chosen, some germ of a common species will fall in and the liquid will become colonized. This has the appearance of spontaneous generation.
The Sowing of Crystals.—Concentrated solutions of various substances, supersaturated solutions of sodium magnesium sulphate, and sodium chlorate are also wonderful culture media for certain mineral organic units—certain crystalline germs. Ch. Dufour, experimenting with water cooled below 0° C., its point of solidification; Ostwald, with salol kept below 39°.5, its point of fusion; Tammann, with betol, which melts at 96°; and, before them, Gernez, with melted phosphorus and sulphur—all these physicists have shown that liquids in superfusion are also media specially appropriate for the culture and propagation of certain kinds of crystalline individuals.
Some of these facts have become classic. Lowitz showed in 1785 that a solution of sodium sulphate could be concentrated by evaporation so as to contain more salt than was conformable with the temperature, without, however, depositing the excess. But if a solid fragment, a crystal of salt, is thrown into the liquor, the whole of the excess immediately passes into the state of a crystallized mass. The first crystal has engendered a second similar to itself; the latter has engendered a third, and so on from one to the other. If we compare this phenomenon with that of the rapid multiplication of a species of microbes in a suitable culture medium, no difference will be perceived. Or perhaps we may note one unimportant difference—the rapidity of the propagation of the crystalline germs as opposed to the relative slowness of the generation of the micro-organisms.
Again, the propagation of crystallization in a supersaturated or superfused liquid may be delayed by appropriate devices. The crystalline individual gives birth, then, to another individual that conforms to its own type, or even to varieties of that type when such exist. Into the right branch of a U tube filled with sulphur in a state of superfusion Gernez dropped octahedric crystals of sulphur, and into the left branch prismatic crystals. On either side were produced new crystals conforming to the type that had been sown.