PROTOPLASM 5 9 



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. 



Sections of fixed and stained cells often show a considerable com- 

 plexity of structure, and various appearances have been often described. 



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. Hardy has imitated these structures by 

 treating perfectly homogeneous colloidal solutions, of egg-white, for 

 example, with various fixatives. 



Professor BUtschli'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 5o°-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 not unlike 

 that of cytoplasm, exhibit movements and streamings not unlike those 

 of Amoebse, and are, in short, mimic cells. Just as a working model 

 may help us to understand the circulation, so these oil-emulsion drops 

 may help us to understand the living cell, by bringing the strictly vital 

 phenomena into greater prominence. 



More recent work, especially with the ultra-microscope, points to the 

 conclusion that the reticular, fibrillar, and other complexities are, in the 

 main, post-mortem effects. There are definite formed bodies, such as 

 mitochondria and various plastids, in many cells, and there is often a 

 deposition of less labile material by the ever-changing protoplasm, but 

 the important fact is that protoplasm is a heterogeneous mixture in a 

 colloid state. 



