48 THE ELEMENTS OF STRUCTURE. 



we may define protoplasm as genuinely living matter — as " the 

 physical basis of life " — we cannot definitely say how much or what part 

 of an Amceba, or an ovum, or any other cell is really protoplasm. We 

 are able to make negative statements, e.,^., the yolk of an egg is not 

 protoplasm, but we cannot make positive statements, or say, This is 

 protoplasm and nought else. Thus, what is spoken of as the structure of 

 protoplasm is really the structure of the cytoplasm. 



In regard to this structure, we know that it is very complex, but we 

 are not sure of much more. For different experts see different appear- 

 ances, even in the same cells. 



Thus some, e.g., Frommann, see an intricate netw'ork or reticulum 

 with less stable material in the meshes; others, e.g., Flemraing, see what 

 looks like a manifold coil of fibrils : and others, e.g., BUtschli, see a 

 foam-like or vacuolar structure. It seems likely that the structure is 

 different at different times, or in different cells. 



Professor BUtschli's belief that the cytoplasm has a vacuolar structure 

 is corroborated by his interesting experiments on microscopic foams. 

 Finely powdered potassium carljonate is mixed with olive oil which has 

 been previously heated to a temperature of 50°-6o° C. an acid from the 

 oil splits up the potassium carbonate, liberates carbon dioxide, and forms 

 an extremely fine emulsion. Drops of this sho\v a structure like that 

 of cytoplasm, exhibit movements and streamings not unlike tiiose of 

 Amcebie, and are, in short, mimic cells. Just as a working model may 

 help us to understand the circulation, so these oil emulsions may help 

 us to understand the living cell,— by bringing the strictly vital pheno- 

 mena into greater prominence. 



