When Perkins’ tractors were in vogue, Dr. Haygarth of Bath, as I have stated in another chapter, had a pair of wooden ones made of precisely the same shape with the orthodox metallic ones, and contrived to color them so that the deception should not be discovered. He then applied them to quite a number of patients, with the same results that followed the use of the genuine tractors, which cost five guineas a pair. Pain was relieved as if by magic, and the lame were made to walk. Their operation in these cases is of course to be accounted for in the same way with the operation of the thermometer in the case just related. Some medical students determined to try the influence of imagination upon a countryman who was going into town to market. They met him one after the other, each telling him how pale and sick he looked. At first, as he felt perfectly well, he paid no regard to it, but after two or three had thus accosted him, he began to think there must be something the matter with him. By the influence of imagination he soon began to feel badly, and to look really pale. And as he still continued to meet persons, who declared themselves struck with his peculiarly sickly and ghastly appearance, he grew worse, and the result was that he sickened and died. I could cite numerous cases illustrative of the influence of the imagination upon the condition of the body, but these will suffice. The physician has constant opportunities for making use of the influence of mental _association_ to much advantage in the management of the sick. He does this almost insensibly in his daily intercourse with his patients, exciting trains of agreeable associations in their minds, varied to suit the mental and moral character of each, thus aiding materially the operation of his remedies.