192 ON GENERATION. 



" Birds which have once copulated almost all continue to lay 

 prolific eggs," but simply " almost all continue to lay eggs ;" 

 the word " prolific" is an addition by Fabricius. But it is one 

 thing to have birds conceiving eggs after intercourse, and another 

 to say that these eggs are fruitful through this intercourse. 

 And this is the more obvious from Aristotle's previous words, 

 where he says, " Nor in the family of birds can those eggs even 

 that are produced by intercourse acquire their full size unless 

 the intercourse between the sexes be continued. And the reason 

 is, that as the menstrual excretion in women is attracted by 

 the intercourse of their husbands, (for the uterus, being warmed, 

 draws the moisture, and the passages are opened,) so in birds 

 it comes to pass that, as the menstruous discharge takes place 

 very gradually, because of its being in small quantity, it cannot 

 make its way externally, but is contained superiorly as high as 

 the waist, and only distils down into the uterus itself. For the 

 egg is increased by this, just as the foetus of oviparous animals is 

 nourished by that which reaches it through the umbilicus. For 

 when once birds have copulated, almost all continue to lay eggs, 

 but of small size and imperfect " and therefore unprolific, for 

 the perfection of an egg is its being fertile. If, therefore, 

 without continued intercourse, not even those eggs that were 

 conceived in consequence of intercourse grow to their proper 

 size, or, as Fabricius interprets it, are " perfected," much less 

 are those eggs prolific which fowls continue to lay independently 

 of intercourse with the male bird. 



But lest any one should think that these words, "for the 

 uterus warmed, draws, and the passages are opened," signify 

 that the uterus can attract the semen masculinum into its cavity, 

 let them be aware that the philosopher does not say that the 

 uterus attracts the semen from without into its cavity, but that 

 in females, from the veins and passages, opened by the heat 

 of intercourse, the menstruous blood is attracted from its own 

 body ; so in birds the blood is attracted to the uterus, warmed 

 by repeated intercourse, whereby the eggs grow, as the foetus of 

 oviparous animals grows through the umbilicus. 



But what Fabricius adds upon that cavity or bursa, in which 

 he thinks the semen of the cock may be stored up for a w r hole 

 year, has been already refuted by us, where we have stated that 

 it contains no seminal fluid, and that it exists in the cock as 



