36 



Methods and Techniques 



in which many factors are still tinknown, 

 and to this extent the transplantation method 

 shares the limitations of many of the isola- 

 tion methods. In addition, furthermore, it 

 has many of its own incident to the complex- 

 ity of variables introduced by using a living 

 organism as host; the results in grafting ex- 

 periments vary according to the species used, 

 according to the size, age and growth rate 

 of the graft and host, according to the site 

 of implantation and so forth. However, in 

 spite of these, indeed perhaps because of 

 them, the method has advantages peculiar to 

 itself, in that it permits, and in fact leads 

 to, the demonstration of interactions at cellu- 

 lar rather than subcellular levels. It thus en- 

 courages some analysis, at least, of that 

 W echselwirkung between cell and environ- 

 ment postulated by Rovix (cf. quotation on 

 p. 31, this section), and the exploitation of 

 the method by Spemann and Harrison has 

 demonstrated the reality of the progressive 

 quality of differentiation which Roux and 

 His before them had postulated. 



The significance, after all, of what a cell 

 can do in isolation can reach its full value 

 only in the light of what the cell does in 

 combination with other cells, and recombina- 

 tion therefore by means of grafting is oblig- 

 atory to clarify interpretation of the results 

 of the isolation and deletion experiments. 

 Without physical and chemical description 

 of the cells and their components, and with- 

 out the knowledge of the separate activity of 

 the cells as ascertained by vital staining and 

 defect and isolation experiments, the results 

 of the transplantation experiments themselves 

 might have little meaning. But it is the re- 

 sults of the transplantation experiments 

 which impute final validity to these others, 

 by presenting as a frame of reference not 

 some chance combination of inert substances 

 but the organized living embryo itself. 



It is when the embryologist attempts to re- 

 fer the phenomena which the transplantation 

 experiments demonstrate as occurring at the 

 cellular level to phenomena with which he 

 is familiar at the subcellular level that he 

 meets his greatest difficulty. But though 

 this problem may seem to present itself more 

 acutely at a time when biochemistry is forg- 

 ing the most rapid advances, it is not in any 

 way a new one, nor was it new when Roux 

 found himself confronted with his passage 

 between the Scylla of the overphysical and 

 the Charybdis of the overmetaphysical inter- 

 pretation of his results (cf. quotation on p. 

 21, Section I). Nor is it any new solution 

 to claim that between these two levels a 



biological plane exists, and to recognize that 

 here, where problems of organization are 

 concerned, all biology works to its least satis- 

 faction. Embryology, as a matter of fact, oc- 

 cupies a more favorable position in this re- 

 spect than many other fields of biology, be- 

 cause it is so fortunate in having had a 

 Spemann and a Harrison whose special gen- 

 ius lay in their ability to probe more deeply 

 than investigators in other areas into the 

 forbidden territories. Their method, as a syn- 

 thetic one rather than an analytic, as a 

 method dealing with mutual interactions in 

 terms of cell and cell, rather than simpler re- 

 action of cell to some less organized entity, 

 has the unique merit to come as close to the 

 biological plane of investigation as has yet 

 been approached. 



For the knowledge to proceed still further 

 into the investigation of these intercellular 

 phenomena and finally into those obscurer 

 supracellular ones which express themselves 

 as organization, embryology must bide its 

 time, but while awaiting the new insight it 

 is clear what its investigators may do. They 

 may continue to elaborate their physical and 

 chemical descriptions as precisely as pos- 

 sible, though recognizing the limitations of 

 these with respect to the fundamental prob- 

 lem of organization. They may specify, as 

 strictly as possible, the conditions under 

 which work is carried out, in the hope of 

 arriving at possible correlations that may 

 eventually provide new clues. And last, but 

 not least, they will do well to remain as 

 closely preoccupied as possible with the 

 living embryo itself. Spemann, it may be re- 

 membered, had the habit of considering the 

 embryo as a Gesprdchspartner who must be 

 allowed to answer in his own language; as 

 a subject, in this sense, rather than a mere 

 object of investigation (cf. Goerttler, '50). 

 The attitude may seem excessively anthropo- 

 morphic, but serves to keep freshly in mind 

 that the embryo, if given the initiative, may 

 have some wise instruction to offer. How in- 

 telligibly the embryo can answer the ques- 

 tions directed towards it depends on the 

 questions asked; these must of course be 

 reduced to simple terms, but they must be 

 terms which the embryo can comprehend. 

 Roux accomplished this, in setting up his first 

 simple alternative; Harrison did so when he 

 isolated the neuroblast, and indeed in many 

 of his subsequent experiments. The most for- 

 midable task of the embryologist is the intel- 

 lectual one of restating the problems, not the 

 technical one of physical manipulation. The 

 embryo makes its replies at a supracellular 



