Abstract
A year ago it was observed that an intravenous injection of a small amount (0.2 c.c.) of immune serum causes the disappearance, within ten minutes'time, of the bacteria from the blood of a rabbit having a pneumococcic septicæmia. It was decided to investigate the above phenomenon in the hope of ascertaining, if possible, the manner of action of anti-pneumococcic serum.
In the light of our results concerning the behavior of typhoid bacilli in the circulation of normal rabbits, we believed it possible that whole rabbit blood plus immune serum killed the pneumococci. Therefore rabbit blood was taken in hirudin; varying amounts of immune serum were added to the hirudin blood; definite quantities of bacteria were added and plates made immediately after starting the experiments, and at intervals for twenty-four hours. The colonies were found much reduced in the tubes containing the immune serum and whole blood, but after twenty-four hours all tubes were “saturated” with bacteria. It was believed that the immune serum plus whole blood produced great reduction in the number of bacteria, but could not cause sterilization.
Later it was deemed advisable to follow with the microscope the processes occurring in the tubes. To our surprise, we found that the bacteria were agglutinated in tubes containing serum in a dilution of 1-500; macroscopically the agglutination titre is 1-80. Thus it appeared that the reduction of colonies was due to the clumping.
It was then surmised that the disappearance of the bacteria from the circulating blood of the rabbit following the injection of immune serum might be due to clumping in vivo and filtration by the capillary systems of the organs. Our investigation of this point gave the following results:
When a rabbit with pneumococcic septicemia is given I C.C. of immune serum intravenously, the cocci are clumped withh forty seconds'time and after two minutes they have left the circulation.
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