It was also seen that recovery from infection in certain diseases was unconnected with phagocytosis.

It had also been demonstrated, by German observers chiefly, that the serum of the blood, the colorless fluid in which the corpuscles float, was itself destructive, and that in an animal rendered immune to a special bacterium the destructive action of the serum on that organism was greatly increased.

In this hostile serum the bacteria often became clumped together in masses, the bodies became swollen, broken up, and finally disintegrated.

This property of the serum was described as due to a substance in the serum called _alexine_, which in the immune animal became greatly increased in amount.

It was even denied by some that phagocytosis of living bacteria took place, and that all those included in the cells were dead, having been destroyed in the first instance by the serum.