Development of Pain-producing Substance in Human Plasma

WE have previously reported 1–3 that inflammatory exudates and fresh plasma produce: (i) pain when applied to the exposed base of a cantharidin blister in man, and (ii) contraction of the isolated rat uterus. Since we find these two actions to run in parallel, we assume that they are due to the same agent, which we term ‘pain-producing substance’. When an inflammatory exudate is collected in a glass syringe, this substance is not at first detectable, but develops within 2–5 min. The same is true of whole blood, with or without anticoagulant.