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It is now well established that para-aminobenzoic acid inhibits the action of sulfonamides on bacteria in vitro and in vivo . (Rubbo and Gillespie, 1940;Selbie, 1940;Woods, 1940). Wiedling (1941) found that para-aminobenzoic acid produced an inhibition of the effect of sulfanilamide, sulfapyridine and sulfathiazole on the fresh water diatom Nitzschia palea var. debilis. Experiments published by Dimond (1941) showed that para-aminobenzoic acid interfered with the action of sulfanilamide on the fungus Trichophyton purpureum. Findlay (1940) has reported that para-aminobenzoic acid inhibited the action of sulfanilamide on a strain of lymphogranuloma venereum.In this communication experiments will be reported which demonstrate the inhibiting effect of para-aminobenzoic acid on the chemotherapeutic activity of sulfamethyldiazine in Plasmnodium lophurae infections in Pekin ducklings. Experiments will also be presented in which, contrary to the experience of Findlay (1940), we were unable to show that para-aminobenzoic acid neutralized the action of sulfanilamide and sulfamethyldiazine on a strain of lymphogranuloma venereum. EXPERIMENTALIn two sets of experiments a total of thirty-eight Pekin ducklings weighing about 50 grams each were inoculated intravenously with 2,000,000 erythrocytes parasitized by P. lophurae.1 Twelve of the infected birds were given 200 mgm. per kgm. of para-aminobenzoic acid together with 200 mgm. per kgm. of sulfamethyldiazine. Eight birds received 200 mgm. per kgm. of para-aminobenzoic acid alone and six birds served as untreated controls. The drugs were incorporated in the food (Startena Mash) so that a reasonably constant blood level was maintained. Therapy was begun on the day of inoculation and continued for 10 days. Beginning on the fourth day following inoculation, the severity of the infection was followed by daily examination of the blood. The results are recorded in table 1. The course of the malaria in the birds receiving paraaminobenzoic acid alone did not differ from that seen in the untreated controls. As the table shows there was a striking difference between the course of the infection in the ducklings given sulfamethyldiazine alone and the course in the birds receiving the drug together with para-aminobenzoic acid. The ducklings receiving sulfamethyldiazine showed few parasites in the blood while those 1 We are indebted to Dr. L. T. Coggeshall for this parasite and for information concerning the technique of handling it in the laboratory. 205

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107induced infection with Type B influenza virus increased resistance of human individuals to for at least one to 4 months. These data infection with virus of Type -4 or Type B. together with those in the preceding paper Further details will be reported subseshow that the same mixed vaccine induced an quently. P Effect of Biotin Deficiency on the Course of Plasmodium l o p h u r eInfection in Chicks. -4.0. SEELER, ~YALTHER H. OTT, AND 1 1 m Y E. GUNDEL. (Introduced by H. Nolitor.) From the M e w k I i i s t i t u t e f o r Tlierapctrfic~ Hcsi < i w I i , Rnliwcc!y, S . J .