SECT. 3] AND EIGHTEENTH CENTURIES 135 



at each end of the egg, which serve for no other end than for Hga- 

 ments to contain the yolk in an equilibrium, that it might not by 

 every moving of the egg be shakt, broke, and confused with the white." 

 Highmore was the first to draw attention to the increase of brittleness 

 which takes place in the egg-shell during incubation, and he holds 

 still to the Epicurean view that the female produces a kind of seed, 

 though he thinks that the chick embryo is nourished in the early 

 stages by the amniotic liquid. 



Perhaps the most interesting reply to Digby from the traditional 

 angle was that of Alexander Ross. In his Philosophicall Touchstone he 

 upheld the Galenic view that the liver must be first formed in genera- 

 tion, for the nourishment is in the blood and the blood requires a liver 

 to make it : ergo, the liver must be the earliest organ. Such arguments 

 could dispense with observations. Ross also mentions Digby's sug- 

 gestion that the "formative virtue" was only a bundle of natural 

 causes, but he claims that the notion was an old one in school- 

 philosophy, being included in the phrase causa causae^ causa 

 causati. 



3-3. Thomas Browne and the Beginnings of Chemical Em- 

 bryology 



There are references to embryology in Sir Thomas Browne's 

 Pseudodoxia Epidemica, or Inquiries into very many vulgar Tenents and 

 commonly received Truths, which was published at this time. The 

 twenty-eighth chapter of the third book contains a number of 

 difficult problems in the embryology of the period, in most cases 

 stated without any solution. "That a chicken is formed out of the 

 yolk of the Egg was the opinion of some Ancient Philosophers. 

 Whether it be not the nutrient of the Pullet may also be considered ; 

 since umbilical vessels are carried into it, since much of the yolk 

 remaineth after the chicken is formed, since in a chicken newly 

 hatched, the stomack is tincted yellow and the belly full of yelk 

 which is drawn at the navel or vessels towards the vent, as may be 

 discerned in chickens a day or two before exclusion. Whether the 

 chicken be made out of the white, or that be not also its aliment, 

 is likewise very questionable, since an umbilical vessel is derived unto 

 it, since after the formation and perfect shape of the chicken, much 

 of the white remaineth. Whether it be not made out of the grando, 

 gallature, germ, or tred of the egg, as Aquapendente informeth us, 



