Abstract
Some time ago in testing the precipitating effect of rabbit serum on various positive and negative colloids I found that such serum precipitated colloidal platinum and colloidal silver to a fair degree. Serum from one rabbit precipitated colloidal platinum completely at 1-100, slightly at 1-200 and not at all at 1-500. This serum precipitated colloidal silver completely at 1-10, partially at 1-100 and not at all at 1-250. After receiving three injections of colloidal platinum in three weeks this rabbit's serum then precipitated colloidal platinum completely at 1-1,000, slightly at 1-1,250 and not at all at 1-1,500. Whereas it precipitated colloidal silver completely at 1-100, slightly at 1-250 and not at all at 1-500.
Serum from another rabbit originally precipitated colloidal platinum completely at 1-50, partially at 1-100 and not at all at 1-250. The same figures held good for colloidal silver. After three injections of colloidal silver during three weeks, this rabbit's serum precipitated the colloidal silver completely at 1-500, partially at 1-1,000 and not at all at 1-1,250, whereas colloidal platinum was completely precipitated at 1-200, partially at 1-500 and not at all at 1-1,000.
In other words the precipitating power of the serum of the first rabbit, after it received three injections of the colloidal platinum, had increased from 1-100 to 1-1,000 or ten times, whereas for the colloidal silver there was only a very slight increase. Serum from the second rabbit, which received colloidal silver, increased its precipitating power from 1-100 to 1-500, whereas for the colloidal platinum, from 1-100 to 1-250. In both these rabbits there was then an increase in the precipitating power of the serum after injection with these colloidal metals, and it would seem that they increased more for the metal injected than for the other.
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