On his removal to Louisville in 1837, to join in the establishment of the rival school, the Louisville Medical Institute, Doctor Yandell taught in the combined chairs of Chemistry and Materia Medica, never failing ably and impressively to perform this arduous duty. Not having any particular taste for so severe a study as practical chemistry, although no one was more impressed with the philosophical beauty and wide practical value of the science, he naturally sought a transfer to a chair more congenial with his tastes and the character of his mind than that of chemistry. This, circumstances prevented until, in 1849, the Trustees of the school--having come to the conclusion that Professor Caldwell had become superannuated--placed Doctor Yandell in the chair of Physiology, for which subject he had a decided taste. This change procured him the animosity of his whilom friend, Doctor Caldwell, who, in his rather unfortunate _Autobiography_ written in his last declining years, indulged in much bitter denunciation of his late colleague. It is much to the credit of Doctor Yandell that, although when this angry publication was fresh from the press he retaliated by showing in ample quotations from the _Autobiography_ some of the weak points in Doctor Caldwell's character, he was disposed in following years, as the writer knows, to extend over these weaknesses the mantle of kindness. Doctor Yandell occupied this chair of Physiology with great credit until he resigned, in 1859, to accept a chair in the Medical School of Memphis, Tennessee. During the Civil War he devoted himself to hospital service. In 1862, he was licensed to preach by the Presbytery of Memphis, and in 1864 was ordained pastor of the Dancyville Presbyterian church. He resigned his pastorship in 1867, and returned to Louisville to resume the practice of medicine, which he had never entirely abandoned during the whole of his professional life.