It will thus be seen that during the space of about 700 years medicine underwent a transformation in Greece. It was first domestic and popular, practiced by shepherds, soldiers,{012} and others; then became sacerdotal; after the Trojan War it was confined to the vicinity of the temples and practiced in the name of some divinity; and finally it was wrapped in mystery and mystic symbolism, where superstition was played upon and credulity made to pay its reward. Down to the time of Hippocrates the Asclep-iadæ rendered some genuine service to science, especially by inculcating habits of observation, in which Hippocrates excelled above all. Later, however, down to the time of the Christian era, medicine in the temples declined, and became, in fact, a system based upon the grossest jugglery. It is time now that we make a systematic attempt to classify events in the history of medicine, and to recognize certain distinct epochs as they have occurred. For this purpose I know of no better arrangement than that of Renouard, which, in the main, I shall follow, at least during the forepart of this book. In this sense he divides the past into three ages, known, respectively, as the _Age of Foundation, the Age of Transition, and the Age of Renovation_. Each of these chronological divisions is subdivided into periods, of which the first contains four:-- AGE OF FOUNDATION. 1. The _Primitive Period_, or that of _Instinct_, beginning with myth, and ending with the destruction of Troy 1184 years before Christ. 2. The _Sacred, or Mystic, Period_, ending with the dispersion of the Pythagorean Society, 500 years before Christ. 3. The _Philosophic Period_, terminating with the foundation of the Alexandrian library, 320 years before Christ. 4. The _Anatomic Period_, ending with the death of Galen, about A.D. 200. THE SECOND AGE, OR THAT OF TRANSITION, is divided into a fifth, or _Greek Period_, ending at the burning of the Alexandrian library, A.D. 640, and a sixth, _Arabic Period_, ending with the revival of letters, A.D. 1400. THE THIRD AGE, OR THAT OF RENOVATION,{013} includes the seventh, or _Erudite Period_, comprising the fifteenth and sixteenth centuries, and eighth, or _Reform Period_, comprising the seventeenth, eighteenth, and nineteenth centuries.