94 GENERAL PHYSIOLOGY 



substratum only is not only unjustified, but even untenable. Not 

 only is it unsupported on any acceptable ground, but it even 

 contradicts facts that may easily be observed. E.g., it is quite 

 impossible to understand how protoplasm in the more or less stiff 

 condition of a framework or network can be capable of streaming 

 and flowing, as can be observed so easily in certain plant-cells and 

 in Amoeba. It is impossible for a solid network to flow in such a 

 manner that the individual particles of its mass mix continually 

 with one another, as may be seen so clearly in Amoeba. If at first 

 sight the theory of the solid consistency may not be incompatible 

 with the behaviour of cells that possess a constant form, it is 

 absolutely so with the phenomena exhibited by naked protoplasmic 

 masses. 



Hence various investigators, especially Berthold ('86) and 

 Btitschli ('92, 1), have recently defended strongly the idea of the 



FIG. 34. a, Vaucheria tube cut open at the upper end ; the protoplasm is flowing out and taking 

 the form of globules. (After Pfeffer.) b, Amceba-cell containing a pale vacuole and various 

 small fat-droplets. 



liquid nature of the cell-contents, and no investigator who is 

 familiar with the phenomena need hesitate to accept this view. 

 Observation of a few facts is convincing of its truth. 



The phenomena of movement, already mentioned, are the strongest 

 proof of the liquid nature of protoplasm. In the protoplasmic 

 strands of plant-cells and in the pseudopodia of Rhizopoda the 

 living substance may be seen flowing like the water of a quiet 

 stream, now slower, now faster, and in different places at unequal 

 rates, so that, as can be observed easily in the constituents enclosed 

 within the ground-mass, the granules, fat-droplets, etc., the particles 

 continually mingle with one another. How would it be possible 

 for a stiff ground-mass to flow like water in a stream ? 



Another thing that throws light upon the liquid consistency of 

 protoplasm is the fact that protoplasmic masses, when oozing out 

 of the cell after its walls have been crushed or cut, form drops and 

 globules. The formation of such drops and globules can be 

 observed very beautifully in the protoplasm of the alga Vaucheria 



