The application of the intracutaneous test with type specific pneumococcic polysaccharide as a guide in serum therapy rests on a basis as sound theoretically as that of the Schick test in the measurement of dermal resistance to diphtheria toxin. In the case of the pneumococcus polysaccharide a positive reaction indicates resistance to the pneumococcus, while in the Schick test a positive reaction is indicative of a lack of such resistance. In either case, however, dermal reactivity is used as a criterion of the immune status of the whole organism.
That pneumococci are not alike was an observation made in 1897 by Bezançon and Griffon,1 who reported serologic differences among morphologically indistinguishable pneumococci. Briefly, the intact pneumococcus cell may be considered to exist as a body, or soma, of bacterial protein, surrounded by a discrete capsule consisting of a carbohydrate substance of relatively complex structure. When released from the intact