Document Type



It was demonstrated by Schott in 1932 that selection for resistance in mice to a standard dose of 5 x 104 S. aertrycke bacteria was effective in decreasing the mortality from 82.3 per cent for the unselected foundation stock to 24.7 per cent in the sixth selected generation. Using the same material as the basis for further study, the complete results for the sixth generation gave a mortality of 22.5 per cent. Further decreases in mortality to 14.7 and 15.6 per cent were observed in the seventh and eighth generations respectively. Groups of mice belonging to the eighth generation when tested with a dose of 2 x 105 organisms gave a mortality of 25.4 per cent. With the 2 x 105 dose the mortalities decreased to 15.8 and 16.2 per cent in the tenth and eleventh generations respectively. Similar sets of mice belonging to the tenth and eleventh generations when tested with a dose of 2 x 106 bacteria gave mortalities of 32.4 and 23.3 per cent respectively. With a dose of 1 x 107 organisms the mortality rose to 40.3 per cent in the eleventh generation. A mortality of 47.2 per cent was observed in the twelfth generation with the dose 1 x 107.

Publication Date


Journal Title

Proceedings of the Iowa Academy of Science





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©1934 Iowa Academy of Science, Inc.



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