'models of living organisms' 89 



were aiming at when they constructed their models. They 

 argued that once the essence of life was shown to be associated 

 with a particular structure, it was only necessary to reproduce 

 that structure, albeit with materials unlike those of the organ- 

 ism, to obtain a system endowed with life — a ' living model '. 



Many people were specially attracted to the artificial 

 reproduction of various structures at that particular time 

 because they were looking for some sort of material frame- 

 work or mechanical structure in protoplasm which would 

 determine all the vital phenomena. It was natural, therefore, 

 to wish to create analogous structures artificially. By mixing 

 and precipitating various substances numerous authors did 

 indeed succeed, on many occasions, in obtaining a micro- 

 scopic picture which strikingly resembled those structures 

 which may be observed in fixed and stained preparations of 

 plant and animal tissues. 



Delighted by the superficial resemblance, these authors 

 enthusiastically proclaimed that they had reproduced living 

 protoplasm artificially. But this was far from being so. Not 

 only were the artificial models lifeless, but even the struc- 

 tures resembling them in the fixed cells were dead. As 

 we have already mentioned, the filamentous, reticular and 

 alveolar structures are artefacts which develop after the death 

 of the cell, as a result of reactions between the proteins and 

 those substances which are used for the fixation and staining 

 of the preparation. The appearance of similar structures in 

 the experiments with models is quite understandable, for 

 here too there takes place just such a precipitation of mixed 

 colloids as occurs during the fixation of protoplasm. This, 

 however, contributes very little to our understanding of life. 

 Scientific interest in this sort of artifical structure, therefore, 

 declined very quickly. 



Nevertheless, in a few scattered laboratories, people con- 

 tinued for a long time to try to ' synthesise life ' by the 

 construction of analogous structural forms. As an example 

 we may cite the experiments of S. Leduc^^ in which he pro- 

 duced so-called ' osmotic cells '. Leduc produced just the 

 same sort of phenomena as Traube but under far more com- 

 plicated conditions. He used small pieces of melted calcium 

 chloride and immersed them in saturated solutions of potash 



