Page:The Works of William Harvey (part 1 of 2).djvu/453

 question, for the principal element under discussion is, not how the semen galli renders the egg prolific, but rather, how does the semen galli fashion and construct the chick from the egg ? Almost everything he adduces in support of his view appears either false or open to suspicion, as is obvious, from the facts stated in our history; for neither is the blind cavity situated at the root of the uropygium or coccyx of the fowl, which he entitles "bursa," destined as a receptacle for the semen of the cock, nor can any semen be discovered there, as we have said ; but the cavity is encountered in the male as well as in the female fowl.

Our authority nowhere explains what he understands by a " spiritual substance," and an " irradiation ;" nor what he means by " a substance through whose virtue the egg is vivi- fied :" he does not say whether it is any " corporeal " or " for- mal" substance, which by "irradiation" proceeds from the semen laid up in the bursa, and, (what is especially required,) constructs a pullet from the egg.

In my opinion, Fabricius does no more here than say : " It produces the chick because it irradiates the egg ; and forms because it vivifies ;" he attempts to explain or illustrate the exceedingly obscure subject of the formation of a living being by means still more obscure. For the same doubt remains untouched, how, to wit, the semen of the cock without contact, an " external efficient " at best, separate in point of place, and existing in the bursa, can form the internal parts of the foetus in ovo, the heart, liver, lungs, intestines, &c., out of the chalazse by "irradiation." Unless, indeed, our author will have it that all takes place at the dictum as it were of a crea- tor seated on his throne, and speaking the words : Let such things be ! namely, bones for support, muscles for motion, special organs for sense, members for action, viscera for con- coction and the like, and all ordered for an end and purpose with foresight, and understanding and art. But Fabricius no- where demonstrates that the semen has any such virtue, no- where explains the manner in which without so much as con- tact the semen can effect such things ; particularly when we see that the egg incubated by a bird of another kind than that which laid it, or cherished in any other way, or in dung,

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