3.56 ON GENERATION.
Neither is there anything contained in the uterus imme- diately after intercourse, which, proceeding from the male, or from the female, or from both, can be regarded as the matter or rudiment of the future foetus. Neither is the semen galli stored and retained in the bursa Fabricii of the hen or else- where, that from thence, as by the irradiation of some spiri- tual substance, or by contact, the egg may be fashioned or the chick constituted from the egg. Neither has the hen any other semen save papules, yelks, and eggs. These obser- vations of ours, therefore, render the subject of generation one of greater difficulty than ever, inasmuch as all the pre- sumptions upon which the two old opinions repose are totally overthrown. The fact is especial, as we shall afterwards demonstrate, that all animals are alike engendered from eggs ; and in the act of intercourse, whether of man or the lower quadrupeds, there is no seminal fluid, proceeding from the male or the female, thrown into the uterus or attracted by this organ ; there is nothing to be discovered within its cavity, either before intercourse, during the act, or immediately after it, which can be regarded as the matter of the future foetus, or as its efficient cause, or as its commencement.
Daniel Sennert, a man of learning and a close observer of nature, having first passed the reasonings of a host of others under review, approaches the subject himself; and concludes that the vital principle inheres in the semen and is almost identical with that which resides in the future offspring. So that Sennert does not hesitate to aver that the rational soul of man is present in his seminal fluid, and by a parity of reasoning that the egg possesses the animating principle of the pullet ; that the vital principle is transported to the uterus of the female with the semen of the male, and that from the seminal fluids of either conjoined, not mixed (for mixture, he says, is applied to things of different species), and endowed with soul or the vital principle a perfect animal emerges. And therefore, he says, the semen of either parent is required, whether to the constitution of the ovum or of the embryo. And having said so much, he seems to think that he has over- come all difficulties, and has delivered a certain and perspicuous truth.
But in order that we should concede a soul or vital principle
