Dialysis blocks the passage of larger substances (for example, red blood cells, large proteins). This replicates the filtering process that takes place in the kidneys when the blood enters the kidneys and the larger substances are separated from the smaller ones in the glomerulus. The two main types of dialysis, hemodialysis and peritoneal dialysis, remove wastes and excess water from the blood in different ways. Hemodialysis removes wastes and water by circulating blood outside the body through an external filter, called a dialyzer, that contains a semipermeable membrane. The blood flows in one direction and the dialysate flows in the opposite.
Water organ by the Greeks, the hydraulis continued to be used through antiquity in the Roman world. In the Middle Ages, Eastern Roman (Byzantine) and Muslim inventors developed, among other pieces, an automatic hydraulic organ (described by the Banu Musa in their 9th-century treatise "Book of Ingenious Devices"), a 'musical tree' at the palace of Khalif al-Muqtadir (ruled 908–32), and a long-distance hydraulic organ that could be heard from sixty miles away (described in the Arabic "Sirr al-asrar" and later translated into Latin by Roger Bacon). By the end of the 13th century hydraulic automata had reached Italy and the rest of