CHANGES WROUGHT IN PATHOLOGY. 107 



minuteness to remain suspended in the liquid an in- 

 definite length of time, then we have a colloidal solution 

 before us. Such a solution is perfectly clear and passes 

 unchanged through the finest filter. We can deduce 

 from the manner of its origin its characteristic properties 

 such a solution represents a suspension of fine elec- 

 trically charged particles, in other words minute elec- 

 trodes. If two gold electrodes connected with a strong 

 electric current are introduced, according to the direc- 

 tions given by BREDIG, into pure water cooled by ice and 

 then are carefully separated until a tiny arc appears, 

 purplish-red clouds begin to emanate from the negative 

 electrode as this goes into solution in the form of fine 

 dust particles, and the result is the production of the 

 beautiful colloidal gold solution which ZSIGMONDY pre- 

 pared previously by chemical means through careful 

 reduction of a gold chloride solution. Partially through 

 use of the chemical method, partially through use of 

 the electrical method, a large number of inorganic 

 colloids have been produced, which have, since GRA- 

 HAM'S fundamental work, formed a much-cherished ob- 

 ject of investigation. But not until recently has it 

 been possible to deduce in a satisfactory way the laws 

 governing their varied behavior from variations in a 

 few characteristics. By utilizing the fundamental work 

 of such investigators as LINDER, PICTON, HARDY, and 

 BREDIG, and many of his own experiments, J. BILLITZER, 

 a Vienna chemist, has been able to show that the chief 

 laws governing and the differences existing between col- 

 loids can all be explained by variations in only three 

 values, namely, the number, size, and electrical charge 

 of the suspended particles, This conception, which 



