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sodium cromoglycate. This effect was not due to a difference between the patients, since when we recalculated the results using the same 11 subjects for both placebo and sodium cromoglycate they were the same. Sodium cromoglycate has a slight phosphodiesterase inhibiting effect, which might explain the differences' 0; however, it has no effect on the histamine response of human bronchial smooth muscle.' We have also shown that sodium cromoglycate has no effect on tracheal smooth-muscle contraction induced by histamine or methacholine."1 It does, however, inhibit allergen contraction of the passively sensitised human tracheal smooth muscles.Our results of the lack of effect of sodium cromoglycate on histamine challenge are consistent with those of Pagelow.'2 He found no difference in the threshold of histamine bronchial reactivity with sodium cromoglycate or phentolamine. In contrast, Kerr et alt7 reported complete protection against histamine with both these agents. We have studied the effect of sodium cromoglycate in vitro on the alpha-receptor contraction of isolated human trachea induced by adrenaline in the presence of propranolol. In this system we are unable to show any inhibition by sodium cromoglycate of alpha-receptor contraction.13

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