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increased phagocytosis (from 28°/, to 38°/,), and that this increase 
is still more obvious in a dilution of 1 : 25000. 
As regards the formate, here too a dilution of 1 : 1000 caused 
an important increase, which continued at 1 : 2000, and which was 
still clearly visible at 1 : 10000. 
An attempt at an explanation of the facts observed. 
‘ 
How must the favourable effect of propionate and of other soaps 
on phagoeytosis be explained ? 
Is the cause the same as that which we adduced to explain the 
effect of lipoid-dissolving substances such as iodoform, chloroform, 
chloral, ete. ? 
Also in the case of these soaps we might think that propionate 
— for convenience sake we shall only mention propionate when we 
should also name the other two soaps which were experimented 
upon — dissolves in the lipoid surface of the phagocytes, softens 
them and facilitates in this way the amoeboid motion. 
Numerous experiments, however, showed that propionate is absolutely 
insoluble in olive-orl. 
We have then tried to find another explanation, and it occurred 
to us that soaps have in a high degree the property of lessening the 
surface tension of oil. 
The reader knows Gap’s experiment: if oil is brought into contact 
with a soap solution, an extremely fine emulsion is formed. 
As far as we know these experiments have only been carried out 
with soaps of higher fatty acids (sapo medicatus or olive-oil 
containing some fatty acid). 
Therefore we have repeated them with soaps containing a smaller 
number of C atoms in their molecules. 
It appeared indeed that the propionate, butyrate and formiate of 
Na have an emulgent effect on olive-oil. The formiate of Na was 
more active than the two others. 
We may conceive that the soaps lay themselves against the surface 
of the phagocytes, reduce the surface-tension, and in this way facilitate 
the amoeboid motion. 
The following observations point in the same direction. 
By way of an illustration we beg the reader to glance at Table II. 
In this series of experiments the leucocyte suspensions, after having 
been in contact with carbon for */, hours at 37°, were suddenly 
cooled down by water at 13°. Then the phagocytes were fixed by 
means of a drop of an osmium-solution. 
