The physical and nervous frailty, which President Eliot had noticed in James during the first winter at the Scientific School, and which later manifested itself so seriously as to interfere with his studies, kept him from enlisting in the Federal armies during the Civil War. The case was too clear to occasion discussion in his letters. He continued as a student at the School and, at about the time the foregoing letter was written, transferred himself from the Chemical Department to the Department of Comparative Anatomy and Physiology, in which Professor Jeffries Wyman was teaching. It was in these two subjects that he himself was to begin teaching ten years later. The next year (1864-65), when he entered the Medical School, Professor Wyman was again his instructor. Jeffries Wyman (1814-1874) was a less widely effective man than Agassiz, but his influence counted more in James's student years than did that of any other teacher. "All the young men who worked under him," says President Eliot, "took him as the type of scientific zeal, disinterestedness and candor." N. S. Shaler, an admirable judge of men, has recorded his opinion of Wyman in his autobiography, saying: "In some ways he was the most perfect naturalist I have ever known ... within the limits of his powers he had the best-balanced mind it has been my good fortune to come into contact with.... Though he published but little, his store of knowledge of the whole field of natural history was surprisingly great, and, as I came to find, it greatly exceeded that of my master Agassiz in its range and accuracy."[26]