PRELIMINARY NOTE 



There have already been certain reviews of work in chemical embryo- 

 logy as a whole, among which those of Paechtner and Schulz are 

 the most valuable. The former dealt almost exclusively with the 

 chemistry of the egg from a static viewpoint, and only devoted a 

 short section to the metabolism of the embryo during its develop- 

 ment, while the latter, though dealing specifically with embryonic 

 metabolism, gave hardly more space to it than Paechtner. In both 

 cases the discussion was little more than a catalogue of references, 

 and in neither case was the literature anything like complete, in- 

 cluding, indeed, less than a tenth of the relevant citations. 



The first review of chemical embryology was written by Grafe in 

 19 10, but, though he outlined several valuable ideas, it is now of 

 small importance. Good information may, however, be found in 

 Aron's monograph on the chemistry of growth and on the mammalian 

 side there are Harding and Murlin. Other, less satisfactory, reviews 

 are by Cazzaniga and Steudel. Finally there is, of course, an 

 immense amount of work which can be found in no review, for 

 investigators have followed the counsel of Godlevski (1910): "Un- 

 sere Kenntnisse hinsichtlich der chemischen Zusammensetztung der 

 Eier noch lange nicht ausreichend sind, so waren weitere Forschungen 

 auf diesem Gebiete auch aus dem Grunde sehr erwunscht weil sie 

 den Ausgangspunkt fiir die Physiologic des embryonalen Stoff- 

 wechsels welcher bisher gleichfalls nur sehr wenig untersucht wurde, 

 bilden mussen". 



Every effort has been made to give an accurate and complete 

 presentation of the data in the Tables of this book and of the 

 experimental conditions under which they were obtained, but 

 investigators should always consult in addition, whenever possible, 

 the relevant original memoirs referred to in the Bibliography. 



