SECT. 3] AND EIGHTEENTH CENTURIES 183 



author, and contains in the second volume what must be regarded 

 as the first detailed account of chemical embryology. I reproduce 

 here the relevant passages in full because of their great interest. 

 It will be noted that they are cast in the form of lecture addresses, 

 as if they had been taken down direct from the lectures of the 

 Professor, a fact which gives them a peculiar charm when it is 

 remembered how many great men must have listened to them, among 

 them Albrecht von Haller and Julien de la Mettrie. In considering 

 what follows, it should be noted that Boerhaave's interest is bio- 

 logical all the time, and that he does not treat the liquids of the egg, 

 as nearly all the chemists before him had done, as substances of 

 curious properties indeed, but quite remote from any question re- 

 lating to the development of the embryo. Another interesting point 

 is that he deals only with the white, and hardly mentions the yolk; 

 this is perhaps to be explained by the Aristotelian theory that the 

 embryo was formed out of the white, and only nourished by the 

 yolk {ex alb fieri, ex luteo nutriri), a theory which was still alive, in 

 spite of Harvey, in the first half of the eighteenth century. If this 

 was what was at the bottom of Boerhaave's mind, then it is obvious 

 that the egg-white would be to him the liquid inhabited more par- 

 ticularly by the plastic force. This, then, is what he has to say about 

 the biochemistry of the egg. 



Op. Chem. in Animalia. [Processus log.] The albumen of a fresh egg is not 

 acid, nor alkaline, nor does it contain a fermented spirit. The white of a fresh 

 egg, separated from the shell, the membranes, and the yolk, I enclose in 

 clean glass vessels, and into each of these I pour different acids, and shake 

 them up, mixing them, and no sign of ebullition appears however I treat 

 them. Therefore I lay these vessels aside. Now in these other two vessels 

 I have two fresh portions of albumen, and I mix with them in one case 

 alkaline salt and in the other volatile alkali. You see they are quiet without 

 any sign of effervescence. Now behold a remarkable thing, in this tall 

 cylindrical vessel is half an ounce of the albumen of an egg and two drams 

 of spirits of nitre, in this other vessel is half an ounce of egg-white, together 

 with four and a half ounces of oil of tartar per deliquium both heated 

 up to 92 degrees. Pray observe and behold, with one movement I pour 

 the alkaline albumen into the acid albumen, with what fury they boil up, 

 into what space they rarefy the mass, so that they stream out of the vessel 

 although it is ten pints in size [decupli capace] . They have scarcely changed 

 their colour. But when the effervescence has abated how suddenly they 

 return to the limits of space occupied before. But now if more egg-white 

 is heated to 100 degrees in a retort [cucurbita] an insipid water containing 



