Counter-current Immunoelectrophoresis (CIE) has been used to detect bacterial capsular polysaccharides in both cerebrospinal fluids and blood serum of children with systemic meningococcal diseases. The sensitivity of the method depends upon the titre of the antisera. It was found that the sensitivity of CIE could not be increased by the method of direct-contact ultraviolet photography. The sensitivity could be increased by one serial dilution, on the average, by the treatment of a 0.25% tannic acid wash for 15 minutes
