The Sushruta Samhita, written in the sixth century BC, comprises 184 chapters that describe 1,120 ailments, 700 therapeutic plants, 64 mineral preparations, and 57 animal preparations. Its creator, Sushruta, is also regarded as the first human to conduct medical surgery on humans. The book also contains extensive information on embryology and human anatomy, directions for venesection, patient placement for each vein, and the preservation of essential tissues (marma). The oldest recorded evidence (9000 years) for the drilling of a living person's human teeth was discovered in Mehrgarh, coupled with pieces of evidence of orthopedic surgery.