The frequency of persistent diarrhea, with or without a known history of a previous acute intestinal infection, stimulated me to investigate the etiologic factors associated with this symptom. With apparently negative results from examination of the stool, a fairly large percentage of patients yielded positive agglutinations in the blood serum for one or more of the organisms of the dysentery group in relatively high titers. Agglutinins have long been known to have an immunologic reaction in the patient's serum against the dysentery bacillus.
Davison 1 in 1920 studied a series of 134 cases of bacillary dysentery in children. He used the agglutination test in addition to bacteriologic methods for diagnosis and considered an agglutination of 1: 50 or above an indication of previous or present dysentery infection. In infants he considered 1: 20 as suggestive. He found that the maximum titer occurred from the seventeenth to the twenty-first day after