Agassiz now returned to Munich to add the title of Doctor of Medicine to that of Doctor of Philosophy. A case of somnambulism, which fell under his observation and showed him disease, or, at least, abnormal action of the brain, under an aspect which was new to him, seems to have given a fresh impulse to his medical studies, and, for a time, he was inclined to believe that the vocation which had thus far been to him one of necessity, might become one of preference. But the naturalist was stronger than the physician. During this very winter, when he was preparing himself with new earnestness for his profession, a collection of fossil fishes was put into his hands by the Director of the Museum of Munich. It will be seen with what ardor he threw himself into this new investigation. His work on the "Poissons Fossiles," which placed him in a few years in the front rank of European scientific men, took form at once in his fertile brain. TO HIS BROTHER. MUNICH, January 18, 1830. . . .My resolve to study medicine is now confirmed. I feel all that may be done to render this study worthy the name of science, which it has so long usurped. Its intimate alliance with the natural sciences and the enlightenment it promises me regarding them are indeed my chief incitements to persevere in my resolution. In order to gain time, and to strike while the iron is hot (don't be afraid it will grow cold; the wood which feeds the fire is good), I have proposed to Euler, with whom I am very intimate, to review the medical course with me. Since then, we pass all our evenings together, and rarely separate before midnight,--reading alternately French and German medical books. In this way, although I devote my whole day to my own work about fishes, I hope to finish my professional studies before summer. I shall then pass my examination for the Doctorate in Germany, and afterward do the same in Lausanne. I hope that this decision will please mama. My character and conduct are the pledge of its accomplishment.