The enzymatic digestion of duck ovalbumin yields precipitating fragments similar to those obtained with hen ovalbumin.
In an anti-ovalbumin serum, the amount of antibody precipitating with the two fragments of degraded homologous ovalbumin and the amount of antibody precipitating with the heterologous ovalbumin are independent.
The absorption of an anti-ovalbumin serum with the heterologous ovalbumin does not remove selectively the antibodies against one or another fragment of the degraded homologous antigen.
The corresponding fragments obtained by digestion of hen and duck ovalbumins give cross-reactions when tested with anti-hen-ovalbumin serum, anti-duck-ovalbumin serum and anti-degraded-hen-ovalbumin serum.
On double diffusion in agar, the cross-reaction between the native ovalbumin and its fragment yields a spur which is shorter than the spur formed by the two native ovalbumins or by the two corresponding fragments.