140 EMBRYOLOGY IN THE SEVENTEENTH [pt. ii 



the former be yellowish in colour and in appearance, yet its con- 

 sistence representeth rather the white, and being sodden, thickeneth 

 like it, growing compact and viscous and may be cut into slices. But 

 the yolk of a perfect eggc being boiled groweth friable and of a more 

 earthy consistence, not thick and glutinous like the white." All of 

 Harvey's observations on the formation of the egg in the oviduct 

 contained in this chapter are interesting, and may with advantage 

 be compared with the studies of Riddle upon the same subject, where 

 the chemical explanation will be found for many of Harvey's simple 

 observations. Harvey's controversy with Fabricius on the question 

 of whether the egg is produced with a hard shell or only acquires 

 its external hardness upon standing in the air, which follows im- 

 mediately on the above citation, is interesting. "Fabricius seemeth 

 to me to be in errour, for though I was never so good at slight of 

 hand to surprise an egge in the very laying, and so make discovery 

 whether it was soft or hard, yet this I confidently pronounce that the 

 shell is compounded within the womb of a substance there at hand 

 for the purpose, and that it is framed in the same manner as the 

 other parts of the egg are by the plastick faculty, and the rather, 

 because I have seen an exceeding small egge which had a shell of 

 its own and yet was contained within another egge, greater and 

 fairer than it, which egge had a shell too." 



Harvey was the first to note that the white of the hen's egg is 

 heterogeneous, in the sense that part of it is much more liquid than 

 the rest, and that the more viscous part seems to be contained in an 

 exceedingly fine membrane, so that if it is sliced across with a knife, 

 its contents will flow out. He also set right the errors of Fabricius, 

 Parisanus and others, by showing that the chalazae were neither the 

 seed of the cock nor the material out of which the embryo was formed, 

 and, most important of all, by demonstrating that the cicatricula 

 was the point of origin of the embryo. He denied, as against popular 

 belief, that the hen contributed anything to the developing egg but 

 heat, "For certain it is that the chicken is constituted by an internal 

 principle in the egge, and that there is no accession to a complete 

 and perfect egge by the Hennes incubation, but bare cherishing and 

 protection; no more than the Hen contributeth to the chickens 

 which are now hatched, which is only a friendly heat, and care, by 

 which she defendeth them from the cold, and forreign injuries and 

 helpeth them to their meat". Whether future work will still affirm 



