acquired their last attenuation in the fourth ventricle, whence they would pass out drop by drop through a round, narrow tube. From this brief _résumé_ of the anatomy and physiology of Galen it will be seen that by the end of the second century of the Christian era immense progress had been made since the foundation of the Alexandrian school, and that it was due to the impetus in the study of anatomy given by Herophilus{042} and Erasistratus, who not only made numerous dissections, but resorted to frequent vivisections. It is even said that Herophilus did not hesitate to employ his knife on live criminals who were subjected to him for experiment; but this has been a popular tradition about almost every anatomist of antiquity, and there is no evidence in confirmation of the unkind rumor, although that such experiments might be legally and justly performed has occurred to the minds of many. But zeal for dissection rapidly cooled off, and Galen barely mentions five or six men who devoted themselves to it in the space of nearly four hundred years down to his time. He speaks of _Rufus_ of Ephesus,--who lived under Trajan of _Marinus_,--who wrote in the beginning of the second century A.D., and of _Quintus_, who instructed his own preceptor. None of them left a reputation, however, approaching that of Herophilus and Erasistratus, with whom Galen alone could compare by the number of his experiments and his discoveries. Galen strove as hard as one of his position might, by example and precept, to awaken in his contemporaries a desire for anatomical knowledge, but could not overcome their indifference. After him the practice of dissection appears to have been lost, either from the redoubled prejudices of the superstitious, who opposed it, or as the result of the apathetic ignorance or the ignorant apathy of the physicians. It has been shown that, during the Hippocratic era and subsequently, the physicians even of primitive times followed more or less by instinct the empirical method. Acron of Agrigentum was a contemporary of Pythagoras, and affirmed that experience is the only true foundation of the healing art. Hippocrates, however, showed himself more anxious to report faithfully clinical facts than to dispute theoretical views.