Note 64 — Chapter II

The doctrine of what may be called the protecting power of some substances is still imperfectly understood, and until late in the eighteenth century, its existence was hardly suspected. It is now known to be connected with the general theory of poisons. See Turner's Chemistry, vol. i. p. 516. To this we must probably ascribe the fact that several poisons which are fatal when applied to a wounded surface, may be taken into the stomach with impunity. Brodie's Physiological Researches, 1851, pp. 137, 138. It seems more reasonable to refer this to chemical laws than to hold, with Sir Benjamin Brodie, that some poisons ‘destroy life by paralysing the muscles of respiration without immediately affecting the action of the heart.’