The Plasmatic Membrane 
193 
IV.— Conclusion. 
The composition of a particle of protoplasm is infinitely more 
complex than that of any other natural or artificial mass, and were 
scientific investigation under the academic control of some all¬ 
knowing power, no doubt man would not yet be allowed to dabble 
in such a difficult matter. However, as it is, we are free to break 
our heads over the difficulties prematurely and we progress spas¬ 
modically by a series of discoveries of isolated truths, for each of 
which its sponsor provides enough experimental support for our 
temporary acceptance of its central significance, but no sufficiently 
clear definition of its boundaries to enable us to piece together the 
fragments to form anything that can be tolerated as a picture of 
the whole. 
It is accordingly by no means easy to correlate in any accurate 
way the results obtained by Czapek with those obtained by 
Lepeschkin, significant as either set is alone. 
Certainly it is beyond question that the chemistry of the proto¬ 
plast belongs to the section of microchemistry. Even were proto¬ 
plasm homogeneous, the thin extension of most vegetable protoplasts 
would make surface-energy an important factor; but when all parts 
have a complex colloidal structure, biochemistry is seen to be almost 
entirely a matter of microchemistry in the sense of Ostwald, and 
the laws of adsorption will dominate the situation. 
The primary difficulty we have to face is our uncertainty of 
exactly how far the comparatively simple principles of surface- 
action and micro-chemistry in a perfect fluid apply without quali¬ 
fication to so complicated a structure as protoplasm. 
Protoplasm is certainly not a perfect fluid, for though it is 
incompressible and non-elastic to prolonged deformation, yet it 
shows some limited elasticity to brief deformation and incomplete 
freedom of its inner particles. Yet though it departs from a perfect 
fluid to this extent it is held to show the predominance of surface- 
tension over internal friction that marks a fluid. Rhumbler 1 has 
investigated the behaviour of the protoplasm of Foraminifera in 
this respect. When the protoplasm creeps outside its test as a 
naked mass and forms a new covering, the edge of the protoplasm- 
film always forms the same definite angle with the substratum—as 
judged by the inclination of the new wall to the old. This can only 
be brought about by surface-tension, and the angle of contact is 
always constant for a given species. 
1 Rhumbler. Archiv. f. Protistenkunde. Bd. I., 1902. 
