I] CHEMICAL EMBRYOLOGY 37 



ducible to terms of pure mathematics; and no object is so reducible 

 except by consciously or unconsciously shutting our eyes to every- 

 thing which differentiates it from anything else. This conscious or 

 unconscious act of abstraction is the very being of the scientific con- 

 sciousness; and it is therefore no matter for pained surprise when 

 science shows a bias towards determinism, behaviourism, and 

 materiaHsm generally". 



By this time the general outlines of this theoretical excursus should 

 have become clear. Embryology, to put it plainly, has been for so 

 many years the happy hunting-ground of vitaHstic and neo-vitalistic 

 theory that the first treatise on the physico-chemical aspect of it 

 could hardly go without some kind of theoretical introduction. 

 "VitaHstic conceptions", said Claude Bernard in 1875, with the 

 voice of authentic prophecy, "can no longer hover over physiology 

 as a whole. The developmental force of the egg and the embryonic 

 cells is the last rampart of vitalism, but in taking refuge there, it 

 transforms itself into a metaphysical concept and snaps the last link 

 connecting it with the physical world, and the science of physiology." 



It is to be hoped that what has now been said will place in a right 

 light the aims of physico-chemical embryology, and provide it, as 

 it were, with its decretals. That they are not false will be the hope 

 of every exact biologist. 



Chemical embryology is now indeed at a critical point in its 

 history. On the one hand, it links up with the morphological work 

 of the classical embryology and the experimental work of the 

 Entwicklungsmechanik school, while on the other hand it has 

 affinities with genetics, a science which is every day becoming more 

 physiological and which will more and more seek for the effects 

 of its factors in the biochemistry of development. Goldschmidt's 

 book, and the work of Dunn, who found a lethal gene in an inbred 

 strain of fowl which caused a regular chick mortaUty at the seven- 

 teenth day of incubation, are important examples of this. Another 

 relationship of chemical embryology is to obstetric medicine, for such 

 problems as the toxaemias of pregnancy will not be solved by Hippo- 

 cratic observation unassisted by a knowledge of the chemistry of 

 the embryo and the placenta. The attention devoted by the Medical 

 Research Council to such problems is an acknowledgment of this 

 fact. Nor is veterinary physiology in a position to do without the 

 aid of chemico-embryological researches, as is shown by the incident 



