PRELIMINARY NOTE 



It is open to anyone to say with some appearance of truth that 

 physico-chemical embryology has no history, since the attempt to 

 unravel the causes of embryological phenomena by physico-chemical 

 means has only recently begun. But such a statement would betray 

 a superficial and jejune mentality. Physico-chemical embryology has 

 its roots in the history of embryology as a whole, and it is those roots 

 which I shall try to uncover in what follows. It must be remembered 

 that morphological must theoretically precede biophysical analysis, 

 as it has actually preceded it chronologically, and to that extent 

 physico-chemical embryology cannot be properly understood without 

 reference to its descriptive husks, and their historical growth. More- 

 over, even in antiquity there are hints that the chemistry of the 

 embryo was dimly envisaged (as in Aristotle, see p. 70). Again, that 

 philosophical problem which we have already considered, plays a great 

 part in the history of embryology, and as we watch the pendulum swing- 

 ing from Democritus to Aristotle, back again over to Herophilus, 

 and back once more to Galen, we almost feel as if we were spectators 

 looking on, like Hardy's spirits, at a great drama, with the movement of 

 which we are powerless to interfere, but knowing that the existence of 

 exact biology depends upon which side wins. Lastly, such unmorpho- 

 logical questions as the respiration and nutrition of the embryo were 

 discussed from the most ancient times, and it is surely no unduly wide 

 interpretation of the word which leads us to include an account of 

 these opinions under the heading of chemico-embryological history. 

 Nor could the present moment be more appropriate for such an 

 historical survey. Embryology is entering a new phase: and on the 

 threshold it is very fitting that some retrospective attention should 

 be paid to the phases which it has already passed through. The 

 events of the past, moreover, throw Hght on those of the future, and 

 this is true not necessarily in Spengler's sense but also because the 

 historical approach to problems actually unsolved protects them, 

 by a kind of gentle scepticism, from too severe a subjection to doc- 

 trinaire presentations. "Die Geschichte einer Wissenschaft ist der 

 Hort ihrer Freiheit; sie duldet ihr keine einseitige Beherrschung", 

 said Louis Choulant in 1842. Theoretical bhnd alleys, such as the 

 final cause, practical blind alleys, such as preformationism and 

 phlogiston, are always able to remind us that we may be mistaken. 



