For studies on the toxic materials, the cells of numerous serological types of group A streptococci, and of a Group B and a Group D streptococcus, were extracted with 0.1 N HCl at 100°C. or by sonic oscillation. The extracts, containing macromolecular components, were subjected to chemical fractionation and purification.

C substance and M protein of Group A streptococci released from the cell by sonic oscillation were toxic to the adrenalectomized rat in quantities of 1 mg./100 gm. rat. Death usually occurred within 2 hours. On the other hand, C substance and M protein released from the cell with HCl at 100°C. were relatively non-toxic to the adrenalectomized rat. The sonic-extracted C substance of streptococcal Groups B, C, and D was also toxic.

The toxic property of the C and M preparations was neutralized in vitro in each case by group and type-specific rabbit antiserum. Heterologous antiserum was without effect. Adrenalectomized rats which received homologous antiserum 18 hours before challenge were also resistant to the toxicity of the C and M preparations.

Trypsin destroyed the toxic effect of the M protein preparations and was without effect on the toxicity of the C substance.

The R antigen and a nucleoprotein component of Group A streptococci, preparations of protein from Groups B and D streptococci, and coagulase from Staphylococcus aureus were all found to be essentially non-toxicic for the adrenalectomized rat. Large quantities of peptone, crystalline albumin, and rabbit serum were also without effect.