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such bold conclusions, since we are completely in the dark about 
the oligodynamic actions of the elements Ferrum, Calcium, Mag- 
nesium. Positive facts, however, prompt us to assume that the 
stimulating effect of the radiations, already discovered, play a prom- 
inent part. 
Most of all our knowledge of the cell-surface as a phase-boundary 
has increased. A lipoid-layer is generally assumed there. Some hold 
this to be an illustration of GrBss’s theorem, according to which 
substances always aggregate on a boundary-layer, which lower the 
surface-tension in situ. This deduction is not admissible, for nothing 
is known about the power of lipoid to lower the surface-tension 
protoplasm—tissuefluid. The data concerning the boundary-layer 
water—air are not immediately applicable to other boundary-layers. 
The determinations made in my laboratory concerning the boundary- 
layer oil—water have shown great differences with the boundaries 
water —air. Therefore, the hypothesis of a lipoid boundary-layer can 
only be admitted as a working-hypothesis not as a deduction. If, 
furthermore, this layer is assumed to be one single layer of molecules, 
after Lanemuir (4), then with a small amount of lipoid some spots 
will remain intact. In this way the so-called mosaic-hypothesis has 
been explained physically. 
For a long time already charges have been assigned to cell-surfaces. 
J. LoeB and Brurner made valuable researches in this direction and 
some time ago J. LorB and his co-workers reduced all to equilibria 
of Donnan. Quite a different theory was set forth by T. P. Frensrra (6) 
in my laboratory. He abandons the membrane-conception, and 
imagines the elements Na, K,Ca aggregated in the form of fixed, 
non-ionised compounds, on a large number of points of the cell- 
surfaces. In that case a solution-potential must be generated on these 
spots according jo Nernst’s theory. From these points some atoms 
will pass into the surrounding tissue-fluid in the form of cations. 
Consequently the loss of positive charge will originate on those spots 
a negative potential, which will increase until the escaping cations 
are in equilibrium with those of the same sort which are already 
present in the tissue-liquid. The various metal points can be of the 
same potential only when the cations in the tissue-fluid are present 
in a certain ratio. From experimental data he calculated this ratio 
for the three elements and found that it agreed with the long 
a 
Ca 
known ratios of the balancing ions in sea-water and in the solutions 
of S. Rinerr. In this striking quantitative concordance he sees an 
affirmation of his theory. 
