SECT. 3] AND EIGHTEENTH CENTURIES 173 



action of the imprisoned air, the fluids of the egg would be forced into 

 the umbiHcal vessels, and the particles composing the embryonic body 

 packed more tightly together. "The internal air appears to perform 

 the same work as the steel plate bent round into numerous coils by 

 which automata are set in motion." 



With this ingenious but erroneous supposition Mayow concludes 

 what is undoubtedly the first great contribution to physiological or 

 biophysical embryology. His views on foetal respiration were soon 

 generally accepted, as the writings of Zacchias, Viardel, Pechlin and 

 John Ray show, but Sponius as late as 1684 was asserting that the 

 lungs of the foetus were functional in utero, absorbing from the 

 amniotic liquid the nitro-aerial particles which P. Stalpartius sup- 

 posed the placenta to be secreting into it. It is interesting to note 

 that by Mayow's own air-pump method Bohn found nitro-aerial 

 particles in the uterine milk in 1686, and Lang found them in the 

 amniotic liquid in 1 704. The problem had by then arrived at a stage 

 beyond which it could not progress in the absence of quantitative 

 methods. 



The year 1675 saw the publication of Nicholas Hoboken's useful 

 treatise on the anatomy of the placenta, and of the English edition 

 of P. Thibaut's Art of Chymistry. I mention the latter here, because 

 of a reference to the special conditions of embryonic life which is 

 found in it. As yet no real help was being given to embryology by 

 contemporary chemistry. 



The Magistery and Calx of Egg-shells. 



Obs. 2. That you must use the eggshells of hens and not of ducks, geese, 

 or turkeys because that hens eggshells easier calcin'd being thinner by 

 reason that a hen is a more temperate animall; waterfowl are hotter and 

 by reason of their heat do concoct and harden their eggshells more than 

 other fowl ; and from thence it comes that you must have a greater quantity 

 of your Dissolvant, employ more heat, and spend more time to calcine 

 the eggs of waterfowl than those of hens. 



About this time also Francis Willoughby published his famous 

 book on birds, an attempt to bring Aldrovandus up to date, in which 

 a good picture is given of the embryological knowledge of the time, 

 although no new observations or theories are given. Another con- 

 temporary review is that of Barbatus. 



In 1677, spermatozoa were discovered, as announced by Hamm 

 and Leeuwenhoek in the Philosophical Transactions of the Royal Society, 



