ON GENERATION. 353 



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, 



23 



