ON GENERATION. 333 



endowed with plastic power, grows into the eye of the egg and 

 the colliquament, from which and in which the primordial or 

 rudimentary parts of the chick, the blood, to wit, and the 

 punctum saliens are engendered, nourished, and augmented, 

 until the perfect chick is developed. Neither is Aristotle's 

 definition of an egg correct, as a body from part of which an 

 embryo is formed, and by part of which it is nourished, unless 

 the philosopher is to be understood in the following manner : 

 The egg is a body, from part of which the chick arises, not as 

 from a special matter, but as a man grows out of a boy ; or an 

 egg is a perfect conception from which the chick is said to be 

 partly constituted, partly nourished ; or to conclude, an egg is 

 a body, the fluids of which serve both for the matter and the 

 nourishment of the parts of the foetus. In this sense, indeed, 

 Aristotle 1 teaches us that the matter of the human foetus is 

 the menstrual blood; " which (when poured into the uterus 

 by the veins) nature employs to a new purpose; viz., that of 

 generation, and that a future being may arise, such as the one 

 from which it springs ; for potentially it is already such as is 

 the body whose secretion it is, namely, the mother/' 



EXERCISE THE FORTY-FIFTH. 



What is the material of the chick, and how it is formed 

 in the egg ? 



Since, then, we are of opinion, that for the acquisition of 

 truth, we cannot rely on the theories of others, whether these rest 

 on mere assertions, or even may have been confirmed by plau- 

 sible arguments, except there be added thereto a diligent course 

 of observation; we propose to show, by clearly- arranged re- 

 marks derived from the book of nature, what is the material 

 of the foetus, and in what manner it thence takes its origin. 

 We have seen that one thing is made out of another (tan- 

 quam ex materia) in two ways, and this as well in works of 

 art, as in those of nature, and more particularly in the gene- 

 ration of animals. 



1 De Gen. Anim. HI), ii, cap. 4. 



