Since the time when Jung and Freud severed their friendship and their collegial relationship, the details and the causes of the rupture have occupied both clinicians and scholars. The intensity of their relationship, and the pain that its breakdown caused them, seem to have driven much of this work, and it remains difficult to understand and assess the differences between them, in theory and in practice. In the service of assessment, we provide here an English translation of Sándor Ferenczi's review of the work by Jung which symbolized the break, his "Wandlungen und Symbole der Libido" (1911/1912). It was the first, and the most thorough and systematic, treatment of Jung's work, written by one of Freud's star followers. We also provide an introduction, which overviews the preparation for a psychoanalytic reply to Jung, based heavily on correspondence, and suggests the need to attend to the differences in clinical methodology implied in the different concepts of the libido held by Freud and Jung.