ON GENERATION. 325 



EXERCISE THE FORTY-THIRD. 



In how many ways the chick may be said to be formed 

 from the egg. 



It is admitted, then, that the foetus is formed from a pro- 

 lific egg, as out of the proper matter, and as it were by the 

 requisite agency, and that the same egg stands for both causes 

 of the chick. For inasmuch as it derives its origin from the 

 hen, and is considered as a fruit, it is the matter : but, in so far 

 as it contains in its whole structure the prolific and plastic 

 faculty infused by the male, it is called the efficient cause 

 of the chick. 



Moreover, not only as Fabricius supposed, are these, namely, 

 the agent and the instrument, inseparably joined in one and 

 the same egg, but it is also necessary, that the aliment by which 

 the chick is nourished, be present in the same place. Indeed, in 

 the prolific egg, these four are found together, to wit, the agent, 

 the instrument, the matter, and the aliment, as we have shown 

 in our history. 



Wherefore, we say, that the chick is formed from the pro- 

 lific egg in all the aforesaid ways, namely, as from matter, by 

 an efficient, and by an instrument ; and moreover, as a man 

 grows out of a boy, as the whole is made up of its parts, and as 

 a thing grows from its nutriment; a contrary thing springs from 

 a contrary. 



For after incubation is begun, as soon as by the internal 

 motive principle a certain clear liquid which we have called 

 the eye of the egg is produced, we say that that liquid 

 is made as it were out of a contrary ; in the same way as we 

 suppose the chyle through concoction to be formed out of its 

 contraries, (namely, crude articles of food,) and in the same 

 way as we are said to be nourished by contraries ; so, from the 

 albumen is formed and augmented that to which we have 

 given the names of the eye and the colliquament ; and in 

 the same manner, from that clear fluid do the blood and 

 pulsating vesicle, the first particles of the chick, receive their 

 being, nutrition, and growth. The nutriment, I say, is by 



