AveustT 9, 1918] 
soap. When an alkali or a salt is added to a 
phenol-water or to a soap-water system the 
“solubility ” of each of the three phases in 
the remaining two changes. A clear “solu- 
tion” of phenol, water and salt (at definite 
temperature) can be obtained only at proper 
concentrations of these three materials. 
Changes in any of them lead to changes in 
viscosity, changes in optical properties, changes 
in the distribution of one or more of the 
“ dissolved ” substances in the other phases, 
ete. This is also true of soap and individual 
proteins as discussed above and of protoplasm 
under physiological and pathological circum- 
stances as noted in our earlier papers. What 
happens depends upon the chemical nature of 
the original substances entering into the mu- 
tually soluble system, their concentration and 
the temperature. 
Applied to protoplasm we incline to the view 
that this consists of a series of hydrophilic 
(protein) colloids which have sucked up 
(“dissolved”) a certain amount of water and 
a certain amount of various salts. The sys- 
tem is not unlike phenol saturated with water 
and containing “ dissolyed” in it various elec- 
trolytes and non-electrolytes. We hope to dis- 
cuss in detail later, older experiments and 
our own which show how, at constant tem- 
perature, physical and chemical variation in 
any one of the substances in such simple 
systems is followed by change in the remain- 
ing ones and this in a fashion identical with 
certain changes observed in_ protoplasm. 
These mutually soluble physico-chemical sys- 
tems show a normal water content (normal 
turgor) which may be decreased (cell shrink- 
age, plasmoptysis) or increased (plasmolysis, 
edema) ; accompanying such there are changes 
in viscosity (drying or swelling of tissues), 
changes in optical properties (“ cloudy” swell- 
ing) and changes in distribution of dissolved 
substances (“vital” absorption or secretion). 
These changes in physico-chemical systems or 
in protoplasm may be brought about by chang- 
ing (1) the fundamental type of the substrate 
itself (as when calcium or magnesium pro- 
teinate is substituted for potassium or sodium 
proteinate), by changing (2) the concentration 
SCIENCE 
147 
of the electrolytes or non-electrolytes acting 
upon the substrate (either by increasing the 
amount of an alkaline metal in a cell, or by 
adding so much that it combines with the 
water of the cell and leads to protoplasmic de- 
hydration through deprivation of “solvent ” 
as first brought out by Hofmeister), or by 
changing (8) the chemical character of the 
salt acting’ upon the substrate (as when mag- 
nesium or iron salts are used instead of salts 
of the alkali metals). Some of these changes 
are reversible (like those produced by alkalies 
or alkali metals, in which ease the correspond- 
ing tissue changes, as “edema” or “cloudy 
swelling,” are also reversible), while others 
are not (in which case the changes in proto- 
plasm, like the effects of a heavy metal; are 
also irreversible or incurable, and the involved 
tissues are said to suffer “death” or “ necro- 
sis”), 
The effect of changes in temperature upon 
these ternary (or more complicated) physico- 
chemical systems is also analogous to the effect 
of temperature upon protoplasm. As mutual 
“ solubility ” may increase or decrease with 
increase in temperature, a change in the sys- 
tem may occur in one or the other direction. 
The clearing of a turbid soap-water-salt or a 
globulin-water-salt system when the tempera- 
ture is raised illustrates the one type of re- 
action, the “ coagulation” of an albumin the 
other. 
v 
This more detailed study on soaps has en- 
abled us also to study further and to verify 
our earlier contentions regarding the condi- 
tions which make for the maintenance and the 
breaking of emulsions. We have previously 
emphasized that oil can not be emulsified in 
water to yield an oil-in-water type of emul- 
sion containing more than a fraction of one 
per cent. of fat, except as a colloid substance 
is present which unites with the water and 
forms a colloid hydrate. The truth of this 
general statement is verified by using as emul- 
sifying agents the soaps described above. The 
lowermost members of the fatty acid series 
(which in water form only molecular solu- 
tions) do not make emulsification at all pos- 
