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 in ancient Greek is often imagined as an automatic organ, but there is no source evidence for it. A hydraulis is an early type of pipe organ that operated by converting the dynamic energy of water () into air pressure to drive the pipes (). Hence its name hydraulis, literally "water (driven) pipe (instrument)." It is attributed to the Hellenistic scientist Ctesibius of Alexandria, an engineer of the 3rd century BC. The hydraulis was the world's first keyboard instrument and was the predecessor of the modern church organ. Unlike the instrument of the Renaissance period, which is the main subject