In all these works it was his object to show that the exegesis of the Alexandrian Jews, and with it that of the early Church Fathers, was dependent on Talmudic exegesis. In this investigation he became a pioneer, and many of his disciples followed him with similar investigations, not only of the Septuagint, but also of the Vulgate and of the Peshitta. A political motive was involved in his study on legal procedure, "Der Gerichtliche Beweis nach Mosaisch-Talmudischem Rechte: Ein Beitrag zur Kenntnis des Mosaisch-Talmudischen Criminal-und Civilrechts: Nebst einer Untersuchung über die Preussische Gesetzgebung Hinsichtlich des Zeugnisses der Juden" (Berlin, 1846). The law of Prussia discriminated against the Jews insofar as the testimony of a Jew against a Christian was valid only in civil cases, and in these only when they involved a sum less than fifty thalers. It was due to Frankel's work, which was cited as an authority in the Prussian Diet, that the new law of 23 July 1847 referring to the Jews, abolished this discrimination. Introduction to Mishnah Frankel's duties as professor of Talmudic literature showed him the necessity of modern scientific text-books on rabbinical literature and archeology. To this necessity are due his introduction to the Mishnah, "Darkei ha-Mishnah" (Leipzig, 1859), with a supplement and index under the title "Tosafot u-Mafteah; le-Sefer Darkei ha-Mishnah" (1867). Of the storm which this book created mention has been made already. It is one of the most valuable attempts at a systematized exposition of the history of early rabbinical literature and theology, and has largely inspired subsequent works of that kind, as those of Jacob Brüll and Isaac H. Weiss. His outline of rabbinical marriage law, "Grundlinien des Mosaisch-Talmudischen Eherechts" (Breslau, 1860), was likewise meant to serve as a textbook on that subject, as was also his attempt at a history of the post-Talmudic literature of sophistry, "Entwurf einer Geschichte der Literatur der Nachtalmudischen Responsen" (Breslau, 1865), which, however, is considered the weakest of his works. Frankel's studies in the history of Talmudic literature had convinced him that the neglect of the Jerusalem Talmud was a serious drawback in the critical investigation of the development of Talmudic law. To this field he determined to devote the remainder of his life. In 1870 he published his introduction to the Jerusalem Talmud under the title "Mebo ha-Yerushalmi" (Breslau). He afterward began a critical edition of the Jerusalem Talmud, with a commentary,