SKIN REACTIONS: WITH FILTRATES OF CULTURES OF KOCH STRAIN OF TUBERCLE BACILLUS GROWING IN LONG'S SYNTHETIC MEDIUM

A report 1 was made recently of the reactions obtained on intracutaneous injection of filtrates of cultures of the Koch strain of tubercle bacillus growing in nutrient broth containing 0.1 per cent of dextrose and 0.1 per cent of dibasic sodium phosphate in place of sodium chloride. Since then, further observations have been made with filtrates of cultures of the same strain growing in Long's synthetic medium. 2 The formula for Long's medium is as follows: A five day growth was passed through Berkefeld N filters and the filtrate diluted with physiologic sodium chloride solution for the skin tests. As a rule, 0.1 cc. of the filtrate, diluted 1: 50, was injected intracutaneously in the forearm, but in persons with a thin skin the arm was more satisfactory. Within twenty-four hours the majority of apparently normal persons develop, at the site of the injection, an area of redness that varies