a1 Glaxo Laboratories, Limited, Greenford, Middlesex
The mouse-protection test is discussed as a routine procedure. It has been shown that the assay is exceptionally subject to variation and that an average slope of 1·47 has been found over a year. With this slope and tests involving 90–180 mice it is possible tobe reasonably sure that a vaccine actually 3 times as potent as needed passes a test which lays down that the lower fiducial limit (P = 0·95) should exceed the specified requirement. For a vaccine only 1·5 times as potent as needed, much more extensive laboratory work would be necessary.
(Received February 16 1956)