THE PROTOPLASMIC SYSTEM 



a great deal of attention has been given to the physical 

 properties of the protoplasmic system. A new and flourish- 

 ing branch of biology, bio-physics, stresses this aspect 

 of the study of life. Some of the more general of these 

 physical properties may be mentioned. 



Protoplasm is a liquid capable of flow. This fluidity 

 can be demonstrated in several ways. First, direct 

 observation shows that in many cells the cytoplasm 

 streams.^ In Amoebae, in many egg-cells, etc., currents 

 can be discerned. Cells which fail to reveal the presence of 

 such currents often show the cytoplasmic granules in intense 

 Brownian movement. Again the fact that in many cells it 

 is possible by very slight centrifugal force to shift and to 

 separate the cytoplasmic inclusions according to their 

 specific weights, demonstrates the liquid nature of proto- 

 plasm. Also, one may compress eggs, draw them out into 

 long strands or otherwise treat them as if they were elastic 

 bags of water. ^ 



The cell-liquid and the various formed bodies suspended 

 in it reveal that protoplasm is both a solution and a suspen- 

 sion, somewhat like milk, for example, which is a solution 

 of water, electrolytes, proteins, sugar, and lipins in which 

 globules are suspended. Protoplasm being largely made 

 up of protein and complex carbohydrates in the colloidal 

 state, is itself in this state. A colloid (literally glue- 

 like^) is matter in the state which can not or can only 

 with difficulty pass through an animal membrane; whereas 

 crystalloids, like cane sugar and common salt, can very 

 readily pass through such membranes. Protoplasm exhib- 



^ Cf. Goette, iS/^, who not only very clearly observed proto- 

 plasmic streaming in an egg but also proffered an interesting 

 hypothesis as to its significance. 



2 Just, igzSa. 



^ Armstrong, 192^, p. 6^6, points out the bad usage of the term, 

 colloid. 



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