Science Record

45

As stated above 45 mice out of 55 mice infected from groups 3, 8 and 9 are still alive 80 days after infection. In order to know if these mice show an immunity against tuberculosis, they were injected intravenously with 0.4 mg of tubercle bacilli together with 60 new mice. The results will be reported in a separate communication.

I am indebted to Professor W. Y. Chang for discussions on cosmic radiation. Also to Mrs. C. S. Fang, Messrs. Y. M. Liu and P. S. Yen for assistance

in the cosmic radiation experiments.

REFERENCES [1] Ong, S. G. 1958 Science Record, New Ser. Il, 9, 289—296. [2] Ong, S. G. 1958 zbid., New Ser. II, 11, 364—372.

Added in proof: Since the submission of the manuscript for publication, i.e. 48 days after the injection with virulent tubercle bacilli, 51 out of 60 control mice were killed, while with those previously injected with tubercle bacilli screened with 3.2, 7.4 and 9.5 cm of lead, the number of deaths was 4, 5 and 1 respectively.

Thus it becomes obvious that the tubercle bacilli exposed to cosmic radiation with 3.2, 7.4 and 9.5 cm of lead screen not only showed a strong attenuated virulence, but also possessed a strong immunizing property against reinfection with virulent tubercle bacilli.

The author