Abstract: It has been reported in the preceding paper that Huang-lien and Hou-p'o showed antibacterial activities against Bacillus anthracis and other bacteria. Their antibacterial actions in vivo were studied here by using guinea pigs artificially infected with Bacillus anthracis. The toxicity of Huang-lien or Hou-p'o was found to be low. Adult guinea pigs of about 300 grams in body weight would stand to:(1) initial dose of 5 ml followed by 2 ml of 1:5 aqueous solution of Huang-lien or Hou-p'o per os every 12 hours for three days,(2) 1 ml dose of 1:5 aqueous solution of Huang-lien intraperitoneally every 12 hours for 4 days,(3) 10 ml dose of 1:5 Hou-p'o aqueous solution intraperitoneally every 12 hours for 4 days,(4) 0.5 ml dose of 1:100 P₂ or 1:200 P₃ aqueous solution intraperitoneally every 12 hours for 4 days,(5) 0.08 gram daily dose of P₂ or P₃ oil emulsion of liquid paraffin or pure olive oil for 4 days when injected subcutaneously every 6 hours. Guinea pigs having received 1000 M.L.D. of Bacillus anthracis subcutaneously died in 39 hours after injection, and those having received 1000 M.L.D. of Bacillus anthracis and drugs, which were administered in a subtoxic dose, gave the following results: (1) Aqueous solutions of 1:5 Huang-lien, 1:5 Hou-p'o, 1:100 P₂ and 1:200 P₃ prolonged the life of infected guinea pigs up to 42-65 hours. (2) The liquid paraffin emulsion of P₂ or P₃ showed no benefit to the infected guinea pigs. (3) The olive oil emulsion of P₂ showed better result which prolonged the life of infected guinea pigs up to 67 hours.