88 A SCIENTIFIC APPROACH 



plasm. More refined methods of investigation came into use. 

 Before it was examined under the microscope the protoplasm 

 was killed or fixed, and then stained. These methods opened 

 up a whole new world of structures and reawakened the hope 

 of visualising the construction of the mechanism of life. 

 The filamentous, reticular and alveolar theories of the struc- 

 ture of protoplasm followed one another very quickly. By 

 the beginning of the twentieth century, however, it had 

 been shown that all the fine structures which could be seen 

 in fixed preparations were artefacts arising after the death 

 of the cell as a result of reactions between the fixative and 

 the proteins of the protoplasm.^® It became quite clear that 

 a study of these structures gives us very little understanding 

 of the organisation of living substance. ^^ 



At about this time and arising out of such theoretical con- 

 siderations, some attempts were made to study life by means 

 of artificially produced living structures, by the construction 

 of models of living protoplasm. Even before this M. Traube-^ 

 had immersed small crystals of potassium ferricyanide in an 

 aqueous solution of copper sulphate and obtained globules 

 surrounded by fine membranes of copper ferricyanide. Under 

 the influence of osmotic pressure these globules grew and, 

 to a certain extent, reproduced the phenomena of the growth 

 of living cells. 



O. BiAtschli^® later made a model which reproduced the 

 movements of a living amoeba. He used drops of olive oil 

 mixed with a solution of potash. As a result of changes in 

 surface tension these drops threw out pseudopodia like 

 amoebae and moved towards solid particles and even en- 

 gulfed them just as amoebae engulf particles of food. Similar 

 very simple models simulating the movement, feeding and 

 division of cells were also produced by L. Rhumbler^" and 

 a number of other workers. 



These models had a certain scientific interest only insofar 

 as the phenomena which occurred in them were based on 

 the same physico-chemical causes as those operating in the 

 living cell. Such models enabled the experimenters to study 

 the phenomenon in question in greater detail under circum- 

 stances which were simpler than those occurring in proto- 

 plasm. This, however, was not what most of these workers 



