On the Respiration of the Faetiis^ etc. 227 



contributes still more to the growth of the chick and 

 to the building up of its structure. For it should be 

 noted that the seminal juices of the egg, colliquated 

 from the beginning of the incubation, formed a fluid 

 body, and that, therefore, among their particles flow- 

 ing hither and thither, there must have been inter- 

 spersed a great number of little spaces. But when 

 the primordial particles go combined together into 

 various parts, they compose no longer a fluid but a 

 solid body, such as is that of the embryo ; and, what 

 is to be chiefly noted, the particles, becoming much 

 more compact, are brought into a smaller space, as 

 was remarked above. 



But since the air enclosed in the ^^^ is always 

 compressing the primogenial juices by its elasticity, 

 that tends to bring it about that the seminal particles, 

 united most closely together, are reduced to the 

 smallest possible space. And this result is at last 

 attained when the particles adapted for forming this 

 and the other parts mutually embrace each other and 

 pass into the body of the embryo, since the primo- 

 genial juices, when converted into the body of the 

 chick, are reduced in bulk by about one half. So 

 that, clearly, that internal air, by compressing and 

 pushing the primordial juices of the Qgg^ appears to 

 perform the same work as the steel plate bent round 

 into numerous coils by which automata are set in 

 motion. 



And, lastly, it is also to be noted, that when the 

 juices of the tgg are forced into smaller bulk by 

 incubation in the manner aforesaid, the shell of the 

 ^gg would scarcely be strong enough to resist the 

 pressure of the external air, unless that internal air, 

 its elasticity in no small degree increased by the heat 

 of the incubating fowl, supported it. 



