1. A washed bacterial suspension of Donovan microorganisms cultivated in the yolk of chick embryos was used as an antigen in intracutaneous tests in 6 cases of granuloma inguinale in the active stage of the disease. These injections were responded to by an extensive erythematous and edematous reaction that reached its height in 24 hours and disappeared within 48 hours later. Four control cases without granuloma inguinale did not react to the injection to any greater extent than would be expected from the slight trauma incident to them. The skin of the reacting patients responded in a similar manner but to a lesser extent to a filtrate of infected yolk. Simultaneous control injections of filtered normal yolk demonstrated that sensitivity to normal yolk was not responsible for the reactions.
2. A mucoid material present in infected yolk, soluble in N/100 NaOH, and precipitable by N/100 HCl was recovered and purified by repeated acid precipitation, extraction with ether, washing in distilled water, and dissolution in N/100 NaOH. We regard this material to be of capsular origin.
3. The presumptive capsular material injected intradermally elicited a somewhat different and milder reaction in patients with active granuloma inguinale, but we regard it as specific.
4. The "capsularrdquo; material in suitable dilution elicited distinct precipitation reactions when mixed with the serum from 18 of 19 cases of active granuloma inguinale. Serum from 1 active case showed no precipitation. Sixty-four serums, including 6 from lymphopathia venereum patients and 18 from Wassermann- or Kahn-positive patients, and 1 from an early chancroid failed to precipitate. Two serums from a total of 66 used as controls showed a precipitate in the presence of the capsular material. These patients gave no history or evidence of granuloma inguinale.
5. The "capsular" material fixed complement in the presence of serum from patients with granuloma inguinale. Serum from 12 of 15 cases of granuloma inguinale demonstrated complement fixation. Three failed to fix complement. Of 19 control serums 18 failed to fix complement in the presence of the capsular material and 1 fixed only a very slight amount of complement. None of these serums nor the capsular material itself was anticomplementary.
6. The high proportion of precipitation and complement fixation reactions obtained from patients with active granuloma inguinale is indicative of a specific immunological relationship of the Donovan microorganism cultivated in embryonic yolk to the disease, granuloma inguinale.
7. We suggest that one or all of these methods might be so standardized as to be of distinct diagnostic value.