So much is certain, and disputed by no one, that animals, all those at least that proceed from the intercourse of male and female, are the offspring of this intercourse, and that they are procreated as it seems by a kind of contagion, much in the same way as medical men observe contagious diseases, such as leprosy, lues venera, plague, phthisis, to creep through the ranks of mortal men, and by mere extrinsic contact to excite diseases similar to themselves in other bodies; nay, contact is not necessary; a mere halitus or miasm suffices, and that at a distance and by an inanimate medium, and with nothing sensibly altered: that is to say, where the contagion first touches, there it generates an “univocal” like itself, neither touching nor existing in fact, neither being present nor conjunct, but solely because it formerly touched. Such virtue and efficacy is found in contagions. And the same thing perchance occurs in the generation of animals. For the eggs of fishes, which come spontaneously to their full size extrinsically, and without any addition of male seminal fluid, and are therefore indubitably possessed of vitality without it, merely sprinkled and touched with the milt of the male, produce young fishes. The semen of the male, I say, is not intromitted in such wise as to perform the part of “agent” in each particular egg, or to fashion the body, or to introduce vitality (anima); the ova are only fecundated by a kind of contagion. Whence Aristotle calls the milt of the male fish, or the genital fluid diffused in water, at one time “the genital and fœtific fluid,” at another, “the vital virus.” For he says[267]: “The male fish sprinkles the ova with his genital semen, and from the ova that are touched by this vital virus young fishes are engendered.”
Let it then be admitted as matter of certainty that the embryo is produced by contagion. But a great difficulty immediately arises, when we ask: how, in what way is this contagion the author of so great a work? By what condition do parents through it engender offspring like themselves, or how does the semen masculinum produce an “univocal” like the male whence it flowed? When it disappears after the contact, and is naught in act ulteriorly, either by virtue of contact or presence, but is corrupt and has become a nonentity, how, I ask, does a nonentity act? How does a thing which is not in contact fashion another thing like itself? How does a thing which is dead itself impart life to something else, and that only because at a former period it was in contact?
For the reasoning of Aristotle[268] appears to be false, or at all events defective, where he contends “That generation cannot take place without an active and a passive principle; and that those things can neither act nor prove passive which do not touch; but that those things come into mutual contact which, whilst they are of different sizes, and are in different places, have their extremes together.”
But when it clearly appears that contagion from noncontingents, and things not having their extremities together, produce ill effects on animals, wherefore should not the same law avail in respect of their life and generation? There is an “efficient” in the egg which, by its plastic virtue (for the male has only touched though he no longer touches, nor are there any extremes together), produces and fashions the fœtus in its kind and likeness. And through so many media or instruments is this power, the agent of fecundity, transmitted or required that neither by any movement of instruments as in works of art, nor by the instance of the automaton quoted by Aristotle, nor of our clocks, nor of the kingdom in which the mandate of the sovereign is everywhere of avail, nor yet by the introduction of a vital principle or soul into the semen or “geniture,” can the aforementioned doctrine be defended.
And hence have arisen all the controversies and problems concerning the attraction of the magnet and of amber; on sympathy and antipathy; on poisons and the contagion of pestilential diseases; on alexipharmics and medicines which prove curative or injurious through some hidden or rather unknown property, all of which seem to come into play independently of contact. And above all on what it is in generation which, in virtue of a momentary contact—nay, not even of contact, save through several media—forms the parts of the chick from the egg by epigenesis in a certain order, and produces an “univocal” and like itself, and that entirely because it was in contact at a former period. How, I ask again, does that which is not present, and which only enjoyed extrinsic contact, come to constitute and order all the members of the chick in the egg exposed without the body of the parent, and often at a long interval after it is laid? how does it confer life or soul, and a species compounded of those of the concurring generants? Inasmuch as nothing, it seems, can reproduce itself in another’s likeness.
EXERCISE THE FIFTIETH.
Of the efficient cause of animals, and its conditions.
That we may proceed in our subject, therefore, and penetrate so far into the knowledge of the efficient cause of animal generation as seems needful in this place, we must begin by observing what instruments or media are devoted to it. And here we come at once to the distinction into male and female; seminal fluid and ovum, and its primordium. For some males, as well as some females, are barren, or but little prolific; and the seed of the male is at one time more, at another time less prolific; because the semen masculinum stored up in the vesiculæ seminales is esteemed unfruitful, unless it is raised into froth by the spirits and ejected with force. And even then perchance it is not endowed with equal fecundating force at all times. Neither are all the germs of yelks in the ovary, nor all the eggs in the uterus made fertile at the same instant.
Now I call that fruitful which, unless impeded by some extrinsic cause, attains by its inherent force to its destined end, and brings about the consequence for the sake of which it is ordained. Thus the cock is called fruitful which has his hens more frequently and surely pregnant, the eggs they lay being at the same time perfect and proper for incubation.
The hen in like manner is esteemed fruitful which has the faculty of producing eggs, or of receiving and long retaining the virtue of prolific conception from the cock. The cluster of germs and the ovary itself are regarded as prolific when the germs are numerous and of good size.