Electrical shock treatment began in the 1700s, and in 1782 a medical electrical machine or induction coil was patented by Edward Nairne. Many machines dating to the 1800s use a small generator and a large bar magnet connected to wheels and a crank that’s wired to two brass handles to shock the patient. Sensitive string galvanometers consisting simply of a single filament hung between the poles of a magnet, were used in 1897 by medical doctors as electrocardiographs to record electric currents generated by heartbeat through electrodes applied to the chest. A similar electroencephalograph was used to measure electrical activity in the brain using electrodes attached to the scalp in 1902. These devises derive from the kymograph, an instrument invented by Wilhem Wundt in the 1840s. Galvanometers were also used as the first electromyographs to detect electrical currents related to muscle action in 1844 and electroretinographs to study electric potential in the retina related to reaction to light intensity in 1849. These recording instruments evolved into bulky, cumbersome and not very practical instruments through the 1800s to be replaced by highly efficient computerized systems by the late twentieth century. The polygraph, well known today as the lie detector, is a physiological instrument designed originally in the 1860s to study interrelationships between the respiratory system, pulse rate and muscle nerve reaction simultaneously and graph the results. It combines a cardiograph, sphygmograph, air tubes and tambour.