SECT, i] EMBRYOLOGY IN ANTIQUITY 67 



and (3) must become something. Now that out of which it is made 

 is the material; this some animals have in its first form within them- 

 selves, taking it from the female parent, as all those which are not 

 born aHve but produced as a scolex or egg; others receive it for a 

 long time from the mother by sucking, as the young of all those 

 which are not only externally but also internally viviparous. Such 

 is the material out of which things come into being, but we now 

 are enquiring not out of what the parts of an animal are made, but 

 by what agency. Either it is something external which makes them 

 or else it is something existing in the seminal fluid and the semen; 

 and this must either be soul or a part of a soul, or something con- 

 taining soul." Aristotle concludes that there is no external shaping 

 influence, but only something or other contained in the embryo itself. 

 To this extent he was wrong, for the influence of the proper physico- 

 chemical environment on the growing embryo is as important as its 

 physico-chemical internal constitution (later he modified his views 

 on this). But now he goes on to deal with the main question, and 

 says, "How then does it (the shaping influence) make the other parts? 

 All the parts, as heart, lung, liver, eye, and all the rest, come into 

 being either together or in succession, as is said in the verse ascribed 

 to Orpheus, for there he says that an animal comes into being in 

 the same way as the knitting of a net. That the former is not the 

 fact is plain even to the senses, for some of the parts are clearly 

 visible as already existing in the embryo wliile others are not; that 

 it is not because of their being too smaU that they are not visible is 

 clear, for the lung is of greater size than the heart, and yet appears 

 later than the heart in the original development". This passage 

 demonstrates that Aristotle had opened hen's eggs at different stages, 

 and was well acquainted with the appearances presented there as 

 early as the third day. He goes on to set forth a further alternative. 

 Agreeing that a continuously new formation of parts takes place, and 

 not merely an unfolding of parts already present in the semen or the 

 menstrual blood, is this brought about by a chain of creations or by 

 one original creation? In other words, does the heart come into being 

 first, and then proceed to form the liver, and then the liver go on 

 to form the lungs, or do they simply appear one after the other without 

 such a creative inter-relationship? Aristotle argues against the former 

 view on the ground that if one organ formed another, the second 

 one would have to resemble the first in some way, which is not the 



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