1. The in vitro rise in the precipitin titer was studied in chickens injected with mammalian serum.

  2. Rise in titer started as early as 11 hours after bleeding and in the majority of cases the peak was reached at 5 to 8 days.

  3. The rise in titer varies but the titers secured within 24 hours were not indicative of the final titers that could be expected.

  4. Two or 3 injections of small quantities of antigen given on alternate days resulted in high titered antisera within 3 to 6 days after the last injection.

  5. Precipitins disappeared almost completely within 3 weeks after a single series of injections, but have persisted for 2 months after a multiple series.

  6. A single injection yielded high titered sera within 5 to 8 days.

  7. A negative phase is produced by reinjections of the homologous antigen.


Supported in part by a grant-in-aid from the Wisconsin Alumni Research Foundation.

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