In the first place, the method by which the authors of that period instilled their astrologic dotage into the minds of their contemporaries varied considerably. Either astrological remarks were here and there interspersed in a work on medical or on astronomical subjects, as was the case, for instance, in the “Opus Quadripartitum” of Ptolemy and also in Galen’s book on the “critical days,” or astrology was treated as a special science in the form of a connected system, as is done, for instance, in the “Iatromathematica” of Hermes Trismegistus. Such textbooks of astrology obtained publicity in large numbers from about the fourteenth century on. Whoever may be inclined to cast a glance into the learned work of Sudhoff will be astonished to observe the extent to which iathromathematics flourished in the second half of the middle ages and at the turning-point of the Renaissance. Still another form was to impart to the public their astrological doctrines in the form of short sentences. We find nothing in such works regarding the intricate calculations and methods by which endeavors were made to fathom the language of the stars, but astrological results were communicated in concise, aphoristic sentences. This was done in the “Centiloquium” of Ptolemy, a work which in a hundred brief sayings brings an epitome of astrological wisdom to market. The work enjoyed the highest esteem in the middle ages. Such a book, therefore, would correspond to that form of modern literary production, which, under the title “Method of acquiring this or that accomplishment within a short period,” is advertised to us modern people in the daily press. Moreover, the “Centiloquium” of Ptolemy had many imitators. Such a work is found, for instance, in Arabic literature, and contains astrologic wisdom condensed into 150 brief sentences by the astrologer Almansor, who furnished the handbook upon request of his ruler; the Arabian, Bethem, has produced a similar work. We find analogous works appearing later in the middle ages. Eventually, the doctrines of astrology were put into neat rhymes; thus, for instance, Heinrich von Rantzau, who departed this life 1598 as governor of Schleswig-Holstein, celebrates in 100 well-turned verses the significance of the planets in relation to the physical and mental welfare of humanity. We shall again refer to this subject when considering astrology of the middle ages. The iatromathematic passages in the above-mentioned writings of Ptolemy, Hermes, and Galen furnished the foundation for all later astrologico-medical theories. For what the middle ages believed regarding the medical importance of the sidereal world, especially of the planets and the zodiac, was nothing but the immediate continuation, or elaboration, of the astrologic teachings of Ptolemy and other authors of the first Christian centuries. In the first place, every portion of the human frame was placed under the influence of a certain celestial body.