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To the Editor.—
In the recent article, "Neurotoxicity of Topically Applied Hexachlorophene in the Young Rat" (Arch Neurol 32:315-319, 1975), Shuman and colleagues found vacuolar encephalopathy more frequently in rats exposed to hexachlorophene than in control rats bathed similarly with a placebo detergent. They concluded that the rats were vulnerable to the effects of hexachlorophene only if bathing began between the 6th and 22nd days of life. If this is true, why did the authors include in the analysis (Table 2) control rats (number not specified) whose first placebo baths were begun between the 23rd and 32nd days of life?Presumably, the "vulnerable" rats (ie, bathing begun between the 6th and 22nd days) in the placebo group were included to rule out confounding causes of vacuolar encephalopathy such as unexpected effects of the detergent base, the bathing procedures, or other laboratory environmental factors. Were the "nonvulnerable" control rats (ie, bathing