In a few respects, however, the Indians independently advanced astronomical science further than the Greeks themselves, and at a later period they in their turn influenced the West even in astronomy. For in the eighth and ninth centuries they became the teachers of the Arabs in this science also. The siddhantas (Arabic Sind Hind), the writings of Aryabhata (called Arjehir), and the Ahargana (Arkand), attributed to Brahmagupta, were translated or adapted by the Arabs, and Khalifs of Bagdad repeatedly summoned Indian astronomers to their court to supervise this work. Through the Arabs, Indian astronomy then migrated to Europe, which in this case only received back in a roundabout way what it had given long before. Thus the Sanskrit word uchcha, "apex of a planet's orbit," was borrowed in the form of aux (gen. aug-is) in Latin translations of Arabic astronomers. After Bhaskara (twelfth century), Hindu astronomy, ceasing to make further progress, became once more merged in the astrology from which it had sprung. It was now the turn of the Arabs, and, by a strange inversion of things, an Arabic writer of the ninth century who had written on Indian astronomy and arithmetic, in this period became an object of study to the Hindus. The old Greek terms remained, but new Arabic ones were added as the necessity for them arose. The question as to whether Indian Medical Science in its earlier period was affected by that of the Greeks cannot yet be answered with certainty, the two systems not having hitherto been compared with sufficient care. Recently, however, some close parallels have been discovered between the works of Hippocrates and Charaka (according to a Chinese authority, the official physician of King Kanishka), which render Greek influence before the beginning of our era likely. On the other hand, the effect of Hindu medical science upon the Arabs after about 700 A.D. was considerable, for the Khalifs of Bagdad caused several books on the subject to be translated. The works of Charaka and Suçruta (probably not later than the fourth century A.D.) were rendered into Arabic at the close of the eighth century, and are quoted as authorities by the celebrated Arabic physician Al-Razi, who died in 932 A.D. Arabic medicine in its turn became the chief authority, down to the seventeenth century, of European physicians. By the latter Indian medical authors must have been thought highly of, for Charaka is repeatedly mentioned in the Latin translations of the Arab writers Avicenna (Ibn Sina), Rhazes (Al-Razi), and Serapion (Ibn Sarafyun). In modern days European surgery has borrowed the operation of rhinoplasty, or the formation of artificial noses, from India, where Englishmen became acquainted with the art in the last century.