Methods and Techniques 



29 



which particular outcomes eventuate will 

 there become available new data and new 

 ideas through which correlations and signifi- 

 cances which currently still elude us may 

 eventually be discerned. 



Granted that the conditions, intrinsic and 

 extrinsic to the embryo, under which obser- 

 vations are made are specified as accurately 

 as possible, the question arises as to their 

 ideal manner of description once they have 

 been obtained. For embryology, the prob- 

 lem of semantics which faces all scientists 

 arises in a particularly desperate form, per- 

 haps at least partly because embryology, 

 never having formulated its own problems 

 nor having developed its own techniques, has 

 adopted descriptive words from the lingo of 

 other sciences. Spemann, it may be remem- 

 bered, concluded his great monograph with 

 a confession that he borrowed words to de- 

 scribe embryonic phenomena which point 

 not to physical but to psychical analogies, 

 to emphasize his conviction that 



these processes of development, like all vital proces- 

 ses, are comparable, in the way they are connected, 

 to nothing we know in such a degree as to those 

 vital processes of which we have the most intimate 

 knowledge, viz., the psychical ones. It was to ex- 

 press my opinion that, even laying aside all philo- 

 sophical conclusions, merely for the interest of exact 

 research, we ought not to miss the chance given to 

 us by our position between the two worlds ('38, p. 

 372). 



Investigators more neutral with respect to 

 this issue use the words induction, determina- 

 tion, regulation, organization, and so forth, 

 borrowed, as Spemann would say, from the 

 psychic sphere, partly out of wonderment at 

 the unexplained powers of regulation of the 

 embryo, but largely for lack of more clearcut 

 or appropriate ones. The problem, however, 

 is not so much of word as of concept; and 

 only when the embryologist can more com- 

 pletely emancipate himself from the domina- 

 tion of other sciences and their techniques, 

 and formulate his problems in his own terms, 

 will he be motivated to create and define such 

 terms with requisite precision. 



Roux seems to have been the first, and the 

 last, to worry over this problem, sufficiently, 

 at least, to be driven to a specific attempt to 

 solve it. He drew up his Terminologie der 

 Entwicklungsmechanik, a discursive text 

 with only the remotest resemblance to our 

 own unfortunate glossaries, with the express 

 aim "das causal-analytische Denken [zu] for- 

 dern und auch das vollkommene Verstandnis 

 der Autoren untereinander [zu] erleichtem" 

 ('12, p. ix). His recognition of the difficulties 



inherent in adapting for Entwicklungsme- 

 chanik terms borrowed from other sciences is 

 perhaps nowhere made clearer than by the 

 fact that he found it necessary to include in 

 the Terminologie two separate definitions in 

 sequence for Tropismus, one for zoological 

 material composed by himself, the other for 

 botanical, contributed by Kiister, one of the 

 botanical collaborators who assisted in the 

 preparation of the book. No modern attempt 

 to emulate the Terminologie has ever been 

 made; no one since Roux has had either 

 the courage or the conceit to try, and modern 

 embryology is still confronted with the old 

 problem of using borrowed terms. Perhaps, 

 however, it is an advantage to the embryolo- 

 gist to be forced to utilize, as a temporizing 

 device, the terminology of physics and chem- 

 istry, since in doing so he must also use their 

 methods and resources. 



It is indisputably by the application of 

 these resources that the greatest advances 

 are being made at the present time. The re- 

 sults of current investigations of structure 

 and ultrastructure by phase-contrast micros- 

 copy and cinemicrography and by electron 

 microscopy; of molecular arrays by polar- 

 ization optics; of chemical constitution and 

 activity by histochemical and immunological 

 techniques, by microspectrography and mi- 

 crospectrophotometry; of the localization, 

 constitution and kinetics of enzymes and en- 

 zyme systems and of other metabolic sys- 

 tems, by microrespirometry, by "biochemical 

 dissection" by antimetabolites and other spe- 

 cific poisons, by modern nutrition studies and 

 by the use of both radioactive and stable iso- 

 topes as tracers; of genetic effects of ioniz- 

 ing radiations — all these will be discussed 

 in ensuing chapters of this book. 



Continuation and elaboration of such phys- 

 ical and chemical descriptions of the em- 

 bryo, of its cells and of their components, are 

 a conditio sine qua nan for further embryo- 

 logical progress. Such description, however, 

 dynamic though it may seem, is essentially 

 structural rather than frmctional, analytical 

 rather than synthetic, and this new mor- 

 phology, like the old, is not able to pene- 

 trate to the core of the problem of organiza- 

 tion. A physical-chemical model of the 

 embryo may ultimately be adequate to rep- 

 resent some phase of what embryonic or- 

 ganization has produced, but as yet there is 

 no assurance that it can reproduce the process 

 by which organization has functioned. Struc- 

 ture, in embryonic material, is not yet ade- 

 quate to "explain" process. 



This may be bound up with the fact that 



