June 22, 1955
Dear Josh,
My secretary is out this week getting married so I will dash this off by hand. I hope you wont [sic] have too much difficulty reading it. The letter doesn't relate to our new antibiotic search but rather to a method of demonstrating relationships between antibiotics i.e. synergism, antagonism or additiveness. I'd like your comments on the following experimental design.
Various proportions of the two antibiotics are made and the amount of the combinations just sufficient to inhibit the organism is determined for each of the mixtures. The results
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may be plotted as below.
[diagram]
The shape of the curve that is obtained tells what the effect of the combination is.
Do you know of any neat way to approach this problem. I am aware of the methods depending on the geometry of one antibiotic diffusing into another like below
[diagram]
Best regards,
Joe