A Study of the Spirochæticidal Action of the Serum of Patients Treated with Salvarsan

1. The serum of rabbits treated intravenously with neosalvarsan, and of syphilitic patients treated intravenously with salvarsan or neosalvarsan, has a definite spirochaeticidal action upon Spirochoeta duttoni. 2. Although this spirochaeticidal action is exerted in vitro, it can be demonstrated only after the treated spirochaetae are injected into susceptible animals. 3. A curative action of the serum of neosalvarsan-treated rabbits is exercised on mice infected with Spirochoeta duttoni. 4. The spirochaeticidal action of the serum of salvarsan-treated rabbits and patients is markedly increased by heating at 56 degrees C. for thirty minutes. 5. The increased spirochaeticidal action produced by heating is due in part to the destruction of some inhibitory substance contained in normal serum and in part to a direct effect of the heat upon the serum and salvarsan mixture. 6. Cerebrospinal fluid does not contain the inhibitory substance present in normal unheated serum.