48 THE ELEMENTS OF STRUCTURE. 



cube. The surface growth always lags behind the increase 

 of mass. Therefore, when the cell has, let us say, quadrupled 

 its original mass, but by no means quadrupled its surface, 

 difficulties set in, waste begins to gain on repair, anabolism 

 loses some of its ascendancy over katabolism. At the limit 

 of growth the cell divides, halving its mass and gaining new 

 surface. It is true that the surface may be increased by out- 

 flowing processes, just as that of leaves by many lobes ; and 

 division may occur before the limit of growth is reached, 

 but, as a general rationale, applicable to organs and bodies 

 as well as to cells, the suggestion of Leuckart and Spencer 

 is very helpful. 



Protoplasm. — Morphological as well as physiological 

 analysis passes from the organism as a whole to its organs, 

 thence to the tissues, thence to the cells, and finally to the 

 protoplasm itself. But although 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.g. 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, describe a network or reticulum, with 

 less stable material in the meshes ; others, e.g. Flemming, describe 

 a manifold coil of fibrils ; and others, e.g. Biitschli, describe a foam- 

 like or vacuolar structure. It seems likely that the structure is different 

 at different times, or in different cells. 



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

 is corroborated by his interesting experiments on microscopic foams. 

 Finely powdered potassium carbonate 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 show a structure like that 

 of cytoplasm, exhibit movements and streamings not unlike those of 

 Amoeba;, 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. 



