Examples of (A) are familiar to all. A hand bathed in hot water is at first much warmer than the other hand that has not been so treated (primary action); but when it is withdrawn from the hot water and again thoroughly dried, it becomes in a short time cold, and at length much colder than the other (secondary action). A person heated by violent exercise (primary action) is afterwards affected with chilliness and shivering (secondary action). To one who was yesterday heated by drinking much wine (primary action), today every breath of air feels too cold (counteraction of the organism, secondary action). An arm that has been kept long in very cold water is at first much paler and colder (primary action) than the other; but removed from the cold water and dried, it subsequently becomes not only warmer than the other, but even hot, red and inflamed (secondary action, reaction of the vital force). Excessive vivacity follows the use of strong coffee (primary action), but sluggishness and drowsiness remain for a long time afterwards (reaction, secondary action), if this be not always again removed for a short time by imbibing fresh supplies of coffee (palliative). After the profound stupefied sleep caused by opium (primary action), the following night will be all the more sleepless (reaction, secondary action). After the constipation produced by opium (primary action), diarrhoea ensues (secondary action); and after purgation with medicines that irritate the bowels, constipation of several days’ duration ensues (secondary action). And in like manner it always happens, after the primary action of a medicine that produces in large doses a great change in the health of a healthy person, that its exact opposite, when, as has been observed, there is actually such a thing, is produced in the secondary action by our vital force.