THE PRESENCE OF PROTECTIVE SUBSTANCES IN HUMAN SERUM DURING LOBAR PNEUMONIA.

These experiments demonstrate that protective substances are usually present in the blood of patients recovering from lobar pneumonia. As a rule, the appearance of protective bodies in the blood, when demonstrable, coincides rather sharply with the period of critical fall in temperature and the disappearance of symptoms. These substances are not present in the blood in any measurable degree before the crisis, but afterward they may reach a considerable concentration. In certain instances, protective substances either become evident some time after the occurrence of the crisis, or cannot be demonstrated at any period of the disease. Experiments in which it is possible to test serum against an homologous strain of pneumococcus yield in the majority of cases evidence of the presence of protective bodies; whereas in those in which stock cultures are used, the serum, as a rule, shows no protection. The development of specific protective substances in the serum of patients with lobar pneumonia suggests that these bodies may play a part in the mechanism of recovery.