and each dipped in a different developer, diagonally across the suspected documents. The developers were wide-spectrum, picking up even such substances as body oils, so that fingerprints and sweat drops often showed up. On the other hand, they missed some specific inks. A bleaching bath removed the stripes. Letters were also checked by infrared and ultraviolet light. Writing in starch, invisible in daylight or under electric light, will fluoresce under ultraviolet. Infrared can differentiate colors indistinguishable in ordinary light and so can pick up, for example, green writing on a green postage stamp. The censorship field stations tested all suspicious letters and a percentage of ordinary mail picked at random, and sometimes all letters to and from a certain 286 THB CUJJJiBKliAKERS city for a week to see if anything suspicious turned up. During the war, about 4,600 suspicious letters were passed along to the F.B.I, and
diffusion tests are used to detect the toxin in sporulation of the cultures seems to be a pre- foods. The commercial kits can detect entero- requisite for toxin production. In 1 to 3 days toxin A, B, C, D, and/or E. either singularly of growth, the organism can produce the or in combination. toxins. The primary toxins are B1, B2, G1, and Fortunately, the organism is not a good G2. B and G indicate that the toxins fluoresce competitor compared with other spoilage blue or green under ultraviolet light, respec- organisms (e.g., Pseudomonas) in raw foods tively. When cows consume B1 and B2 toxins, such as ground beef and fish. However, in the they can modify the toxins and excrete the absence of competitors, such as in salty food toxins as M1 and M2 in milk. (e.g., ham) or processed foods (e.g., pro- Spores of these molds are ubiquitous; the
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