_Meletius_ was a Christian monk who lived in the fourth century, according to some authorities, but it is probable that he belonged to a later period, the sixth or seventh century. He wrote on the nature of man, but the book is of no value as a contribution to physiology. _Nemesius_, Bishop of Emissa, at the end of the fourth century wrote a book called "De Natura Hominis," and came very close to two important discoveries, namely, the functions of the bile and the circulation of the blood. Of the former, he wrote, "The yellow bile is constituted both for itself and for other purposes; for it contributes to digestion and promotes the expulsion of the excrements; and therefore it is in a manner one of the nutritive organs, besides imparting a sort of heat to the body, like the vital power. For these reasons, therefore, it seems to be made for itself; but, inasmuch as it purges the blood, it seems to be made in a manner for this also."[28] With reference to the circulation of the blood, Nemesius wrote: "The motion of the pulse (called also the vital power) takes its rise from the heart and chiefly from its left ventricle. The artery is with great vehemence dilated and contracted, by a sort of constant harmony and order, the motion commencing at the heart. While it is dilated it draws with force the thinner part of the blood from the neighbouring veins, the exhalation or vapour of which blood becomes the aliment for the vital spirit. But while it is contracted it exhales whatever fumes it has through the whole body and by secret passages, as the heart throws out whatever is fuliginous through the mouth and nose by expiration."[29] This book was first translated into English in 1636. Nemesius also wrote on religion and philosophy. In regard to his medical writings, although he did not go far enough to anticipate the discovery of Harvey, his contribution to medical science was remarkable. _Ætius_ was born in Mesopotamia and lived at the end of the fifth or the beginning of the sixth century. He studied at Alexandria, and settled at Constantinople, where he attained to the honour of court chamberlain, and physician to the Emperor Justinian. He was the first notable physician to profess Christianity. In compounding medicines, he recommended that the following prayer should be repeated in a low voice: "May the God of Abraham, the God of Isaac, and the God of Jacob deign to bestow upon this medicament such and such virtues." To extract a piece of bone sticking in the throat, the physician should call out loudly: "As Jesus Christ drew Lazarus from the grave, and as Jonah came out of the whale, thus Blasius, the martyr and servant of God, commands, 'Bone, come up or go down.'"