1. Antipneumococcus serum possesses the power of inhibiting for a certain period of time the multiplication of pneumococci.
2. It also has the capacity of inhibiting the proteolytic and glycolytc functions of pneumococci.
3. This power is acquired for the first time or appears in increased amounts in human serum at the time of crisis in lobar pneumonia.
4. The retardation of bacterial growth is thought to be dependent upon the inhibition of metabolic function due to the presence of anti-enzymotic substances in antipneumococcus serum. To this phenomenon we have applied the term antiblastic immunity.