These were gradually replaced by the letter R, or its astrological modification ℞, which was equivalent to _Recipe_, Jupiter,--Take, O Jupiter! We are told that the astrological signs were thus brought into use during Nero's reign, and that the practice of Medicine was then and afterwards regulated by the government. It is not improbable that Christian physicians were obliged to follow the example of their heathen professional brethren in prefixing to their prescriptions invocations to Jupiter.[157:1] Johann Michael Moscherosch (1600-1669), a learned German writer, offered a unique explanation of the meaning of the medical symbol ℞, which he maintained to be equivalent to _Rec_, an abbreviation for _per decem_. And he explained the significance of the latter as being that one prescription out of ten might be expected to prove beneficial to the patient. It is certain, wrote Dr. Otto A. Wall, in his volume, "The Prescription," that pharmacies for the dispensing of medicines on physicians' prescriptions were already in existence at the ancient Spanish city of Cordova, and at other large municipalities under the control of the Arabs, previous to the twelfth century. And as early as 1233, pharmacy laws had already been passed in the Two Sicilies. By that time, it appears probable that medical prescriptions were no longer mere superstitious formulas, but that they contained directions for compounding material remedies having more or less medicinal virtues. Modern medical prescriptions may be classed as lineal descendants of the healing-spells of former ages. In the most ancient known pharmacopœia, a papyrus discovered about the year 1858 in the Necropolis at Thebes, and believed to date from the sixteenth century B. C., no invocations or symbols are found, nor were the latter generally employed as prefixes to medical formulas prior to the first century A. D.; when their use appears to have originated among the Greeks and Romans, and the custom has continued until the present day. At the time of the alchemists, in the sixteenth century, "the influence of the Church on the minds of men, or perhaps the fear of the Inquisition, led physicians to adopt an invocation to the Christian God; just as they abbreviated a prayer to crossing themselves with their fingers over their foreheads and breasts, so they contracted the invocation to the sign of the cross as a superscription."[158:1] Thus instead of the sign ℞ some physicians began their prescriptions with the Greek letters Α. Ω.; or the letters J. D. for _Juvante Deo_, C. D. for _Cum Deo_, or N. D. for _Nomine Dei_.