Wandlungen und Symbole der Libido. Beiträge zur Entwicklungsgeschichte des Denkens.

Reprinted in book form, Leipzig, F. Deuticke, 1912. Jung was among the first to support Freud’s views on psychoanalysis, and was considered by Freud to be his most brilliant pupil. Jung applied psychoanalytic theory to the study of myths, developing the idea of the collective unconscious. In 1913 Jung broke away from Freud and founded the school of analytical psychology. English translation by Beatrice M. Hinkle as Psychology of the unconscious: A study of the transformations and symbolisms of the libdio. A Contribution to the history of the evolution of thought. (New York: Moffat, Yard, 1916). In 1952 Jung published a thoroughly revised version of the work, translated into English in 1956 as Symbols of Transformation, and issued as volume five of Jung's Collected Works

Digital facsimile of the 1912 edition from the Hathi Trust at this link; of the 1916 English translation at this link.