ON GENERATION. 205 



now be given more particularly, and we shall begin from without 

 and proceed inwards. 



" The external covering of the egg, called by Pliny the cortex 

 and putamen, by Quintus Serenus the testa ovi, is a hard but 

 thin, friable and porous covering, of different colours in different 

 cases white, light green, speckled, &c. All eggs are not fur- 

 nished with a shell on their extrusion: the eggs of serpents have 

 none; and some fowls occasionally, though rarely, lay eggs that 

 are without shells. The shell, though everywhere hard, is not 

 of uniform hardness; it is hardest towards the upper end." 

 From this Fabriciusi opines that we are to doubt as to the 

 matter of which, and the season at which the shells of eggs are 

 produced. Aristotle 2 and Pliny 3 affirm that the shell is not 

 formed within the body of the fowl, but when the egg is laid ; 

 and that as it issues it sets by coming in contact with the air, 

 the internal heat driving off moisture. And this, says Aristotle, 4 

 is so arranged to spare the animal pain, and to render the pro- 

 cess of parturition more easy. An egg softened in vinegar is 

 said to be easily pushed into a vessel with a narrow mouth. 



Fabricius was long indisposed to this opinion, " because he 

 had found an egg within the body of the fowl covered with a 

 hard shell; and housewives are in the daily practice of trying the 

 bellies of their hens with their fingers in order that they may 

 know by the hardness whether the creatures are likely to lay 

 that day or not." But by-and-by, when " he had been assured 

 by women worthy of confidence, that the shells of eggs became 

 hardened in their passage into the air, which dissipates a cer- 

 tain moisture diffused over the egg on its exit, fixing it in the 

 shell not yet completely hardened;" and having afterwards 

 " confirmed this by his own experience," he altered his opinion, 

 and came to the conclusion, " that the egg surrounded with a 

 shell, and having a consistency betwixt hard and soft, hardened 

 notably at the moment of its extrusion, in consequence, ac- 

 cording to Aristotle's views, of the concretion and dissipation of 

 the thinner part of a certain viscid and tenacious humour, 

 bedewed with which the egg is extruded; sticking to the recent 

 shell this humour is dried up and hardened, the cold of the 



1 Loc. cit. p. 13. a Hist. Anim. lib. vi, c. 2, et de Gen. Anim. lib. i,-c. 8. 



3 Hist. Anim. lib. x, c. 52. 4 De Gener. Anim. lib. iii, c. 2. 



