Figure 1.

Mean (+SE) change of gamma globulin levels at approximately 3 weeks from inoculation of SRBCs of male swallows whose tails were unmanipulated (Control I), cut and reglued (Control II), and shortened or elongated by 20 mm, that survived (white bars) and did not survive (black bars) until the breeding season following that of inoculation. Measurement unit of gamma globulins is the percentage of gamma globulins relative to whole protein plasma content. Change is expressed as difference between value at recapture and value at first capture. Numbers are sample sizes.