3.  Change the kinds of stimulus.  The habits acquired by the constitution depend on such nice circumstances, that when one kind of stimulus ceases to excite the sensorial power into the quantity of exertion necessary to health, it is often sufficient to change the stimulus for another apparently similar in quantity and quality.  Thus when wine ceases to stimulate the constitution, opium in appropriate doses supplies the defect; and the contrary.  This is also observed in the effects of cathartic medicines, when one loses its power, another, apparently less efficacious, will succeed.  Hence a change of diet, drink, and stimulating medicines, is often advantageous in diseases of debility.

4.  Stimulate the organs, whose motions are associated with the torpid parts of the system.  The actions of the minute vessels of the various parts of the external skin are not only associated with each other, but are strongly associated with those of some of the internal membranes, and particularly of the stomach.  Hence when the exertion of the stomach is less than natural, and indigestion and heartburn succeed, nothing so certainly removes these symptoms as the stimulus of a blister on the back.  The coldness of the extremities, as of the nose, ears, or fingers, are hence the best indication for the successful application of blisters.

5.  Decrease the stimulus for a time.  By lessening the quantity of heat for a minute or two by going into the cold bath, a great accumulation of sensorial power is produced; for not only the minute vessels of the whole external skin for a time become inactive, as appears by their paleness; but the minute vessels of the lungs lose much of their activity also by concert with those of the skin, as appears from the difficulty of breathing at first going into cold water.  On emerging from the bath the sensorial power is thrown into great exertion by the stimulus of the common degree of the warmth of the atmosphere, and a great production of animal heat is the consequence.  The longer a person continues in the cold bath the greater must be the present inertion of a great part of the system, and in consequence a greater accumulation of sensorial power.  Whence M. Pome recommends some melancholy patients to be kept from two to six hours in spring-water, and in baths still colder.

6.  Decrease the stimulus for a time below the natural, and then increase it above natural.  The effect of this process, improperly used, is seen in giving much food, or applying much warmth, to those who have been previously exposed to great hunger, or to great cold.  The accumulated sensorial power is thrown into so violent exertion, that inflammations and mortifications supervene, and death closes the catastrophe.  In many diseases this method is the most successful; hence the bark in agues produces more certain effect after the previous exhibition of emetics.  In diseases attended with violent pain, opium has double the effect, if venesection and a cathartic have been previously used.  On this seems to have been founded the successful practice of Sydenham, who used venesection and a cathartic in chlorosis before the exhibition of the bark, steel, and opiates.