1. The salt dissociation and barium hydroxide-barium chloride methods are extended to the preparation of highly purified antibody solutions from specific precipitates derived from Type III and Type VIII antipneumococcus horse sera and a low grade polyvalent bovine serum. Analytically pure precipitin (agglutinin) was obtained from the last, and Types I, II, and III antibodies were separated.

2. Difficulties connected with the application of the methods to Type I antipneumococcus rabbit sera are described, as is also the purification of antibody from low grade pig and sheep sera.

3. The dissociation of antibody by both methods from Type I pneumococci agglutinated in antisera produced in the horse, rabbit, pig, and sheep, is described and its advantages discussed.

4. Certain theoretical aspects of the work are also discussed.

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