ment-mediated hemolysis of 1:10 diluted fresh guinea pig and human serum; at least twice as much SPS was required to reduce complement activity in 1: 2 diluted human serum. The coagulation of 90 and 20% human blood was inhibited by 250 and 125 Ag of SPS per ml, respectively. When added to fresh human serum, SPS precipitated beta iC-globulin (C3), C4, beta lipoproteins, immunoglobulin IgG, IgM, and IgA, though incompletely.

Two spot-indole reagents, p-dimethylaminobenzaldehyde (DMABA) and pdimethylaminocinnamaldehyde, were evaluated quantitatively. Although fourfold less sensitive, DMABA proved to be more stable and economical.