224 Mayow 



placed in every Q,gg is altogether useless and super- 

 fluous. But in order to understand the function of 

 that air, it must first be noted that the seminal juices 

 of the egg when colliquated by incubation are not 

 rarefied or expanded, but are on the contrary con- 

 densed and forced into a narrower space than before. 

 For we remark that the aforesaid cavity is greatly 

 enlarged after a few days' incubation, as will be 

 manifest if the blunt end of the egg is perforated. 

 But this would not at all be the case unless the juices 

 which filled nearly the whole of the Q^g before 

 incubation were subsequently, by the incubation, 

 condensed and made to occupy less space than before. 

 In fact the humours of the egg are contracted after 

 they have passed into the body of the chick, to about 

 a half less than they*" were at first, since the cavity 

 enlarges under incubation to about half the size of the 

 whole Qgg, 



But now let us consider briefly how it is that the 

 juices of the egg are condensed to such a degree by 

 incubation ; and it is to be noted that things may be 

 condensed in various ways : 



I. If vacant spaces numerously interspersed among 

 the particles of the thing to be condensed are 

 diminished or even removed by the particles 

 approaching each other. But it is not probable that 

 the juices of the o,^^ are condensed in this way only. 

 For it is by no means to be believed that as much 

 empty space should be distributed among the juices of 

 the egg as is required for contracting them to the 

 extent of about one half. For if such were the case 

 the juices of the egg would contract very much on 

 account of the pressure of the atmosphere when the 

 shell is perforated. Yet this does not at aP. take 

 place. 



