RESUMEN
In the process of obtaining PPD-tuberculins we studied some carbonic acids thus replacing asparagine with them in the original medium of Sauton. The following carbonic acids were used: dibasic saturated carbonic acids--oxalic, malonic and succinic; dibasic non-satured carbonic acids--maleic and fumaric; the dibasic oxycarbonic acid--tartaric. Each of the above mentioned acids was in a concentration equivalent to that of the asparagine in the original Sauton's medium. The tuberculins were obtained through the precipitation of the filtrate of killed liquid cultures by trichloracetic acid. The bovine and avian PPD-tuberculins so obtained with the different carbonic acids were assayed on sensitized guinea pigs and hens together with standard tuberculins. The results obtained from the application of the PPD-tuberculins of carbonic acids are almost identical with the ones of the standard PPD-tuberculins. The experimental and standard bovine PPD-tuberculins used contain 50,000 ISU in 1 ml and the avian experimental and standard PPD-tuberculins contain 25,000 ISU in 1 ml. The results obtained give us reason to consider that some of the above mentioned carbonic acids could be used for the production of PPD-tuberculins.