145 
1918-19.] On the Mode of Action of Metal Sols. 
mechanical action as the trajectory of the particles played an important 
part in the pharmacological effect, it would be expected that all suspensoids 
would be equally effective, which is not the case. 
Surface Phenomena . — An attempt has been made to explain certain 
important pharmacological actions by alterations in surface energy, and 
in the case of certain emulsoids it is probable that such an action plays 
a part. But surface actions of this type, dependent on adsorption, 
questionably occur under similar conditions in the case of suspensoids, 
and ultramicroscopic observations show no adhesion at least of the larger 
particles of a silver sol to the bacilli. 
Electric Charge . — Nor does the pharmacological action appear to depend 
on the kind of electric charge on the particles. The negative electrical 
charge of a colloidal silver sol was shown by Hardy’s modification 
of Whetham’s method,* and the quantity of an alum sol necessary 
to reverse the charge and convert the sol into an electro-positive sol 
was determined. It was found that electro-negative and electro-positive 
sols produced the same antiseptic action. 
Bacillus typhosus. 
Amount of Sol added to 5 c.c. 
of Culture Medium. 
Result after Incubation for 
24 hours. 
48 hours. 
72 hours. 
Electro-negative : — 
0'8 c.c. .... 
0 
+ 
i-o „ .... 
0 
0 
0 
Electro-positive : — 
0 8 c.c. .... 
0 
+ 
i-o „ .... 
0 
0 
1 
0 
Against B. coli communis the electro-positive sol seemed to be slightly 
the more active. 
Catalytic Power . — This was not systematically determined, as preliminary 
experiments seemed to show that it was insufficient to explain the effects 
obtained in this class of experiment. Electragol, for example, was much 
more powerfully catalytic when compared with the electrolyte-free sol 
than the relative bactericidal actions would account for. In the absence 
of surface effects it is difficult to understand how catalysis alone could 
play a predominant part. 
VOL. XXXIX. 
* Journ. of Physiol., vol. xxxiii, p. 289 (1905). 
10 
