The diviners used certain incantations to cure the sick, but the healing art among the Incas was really in the hands of learned men. Those _Amautas_ who devoted themselves to the study of medicine had, as Acosta bears testimony, a knowledge of the properties of many plants. The febrifuge virtues of the precious _quinquina_ were, it is true, unknown, or only locally known. But the _Amautas_ used plants with tonic properties for curing fevers; and they were provided with these and other drugs by an itinerant caste, called Calahuayas or Charisanis, who went into the forests to procure them. The descendants of these itinerant doctors still wander over South America, selling drugs.[1198] The discovery of a skull in a cemetery at Yucay, which exhibits clear evidence of a case of trepanning before death, proves the marvellous advances made by the Incas in surgical science. [Illustration: RUINS AT CHUCUITO. [After a drawing in Squier’s _Primeval Monuments of Peru_, p. 17, showing a wall of hewn stones, with an entrance. The enclosed rectangle is 65 feet on each side,—“a type of an advanced class of megalithic monuments by no means uncommon in the highlands of Peru.” Cf. Squier’s _Peru_, p. 354.—ED.]] The sovereign was the centre of all civilization and all knowledge. All literary culture, all the religious ceremonial which had grown up with the extension of the empire, had the Inca for their centre, as well as all the military operations and all laws connected with civil administration. Originally but the _Sinchi_, or chief of a small _ayllu_, the greatness of successive Incas grew with the extension of their power, until at last they were looked upon almost as deities by their subjects. The greatest lords entered their presence in a stooping position and with a small burden on their backs. The imperial family rapidly increased. Each Inca left behind him numerous younger sons, whose descendants formed an _ayllu_, so that the later sovereigns were surrounded by a numerous following of their own kindred, from among whom able public servants were selected. The sovereign was the “_Sapallan Inca_,” the sole and sovereign lord, and with good reason he was called _Huaccha-cuyac_, or friend of the poor.