Moreover, we often are apt to learn something from even the most ignorant of these men. Rush investigated the nature of a cancer-cure by not refusing to meet and talk with one of this kind;[28] Fothergill learned from an old, unlicensed practitioner that there was a knowledge important to the physician beyond that picked up in the pathological laboratory or the study of microscopy; and that the practiced eye of an otherwise unlearned man could detect that there were general physical signs that negatived the unfavorable prognosis suggested by the presence of tube-casts.[29] It is related of Sir Isaac Newton, that while riding homeward one day, the weather being clear and cloudless, in passing a herder he was warned to ride fast or the shower would wet him. Sir Isaac looked upon the man as demented, and rode on, not, however, without being caught in a drenching shower. Not being able to account for the source of information through which the rustic had gained his knowledge, he rode back, wet as he was, to learn something. "My cow," answered the man, "always twists her tail in a certain way just before a rain, your Worship, and she so twisted it just before I saw you."[30] Although twisting cow-tails do not figure in his "Principia," it is very probable that such a lesson was not without its remote effects on a mind like Newton's. A spider taught a lesson to one of Scotland's kings; so that one man may learn something from another. Professor Letenneur, of the Medical School of Nantes, in his "Causerie a propos de la Circoncision," mentions that the Convent of Saint Corneille, in Compiegne, claims to possess the identical instrument with which the Holy Circumcision was performed. Such a holy relic must have been unusually potential in performing many miracles.