1. An electroencephalographic system for the on-line conditioning of signals representing brain waves and representing muscle artifact, comprising a plurality of electrodes adapted to be removably attached to the head of a patient, a plurality of amplifiers each connected to a different pair of said electrodes, a matrix multi-channel display and recorder which in response to digital signals displays a copy of a plurality of the brain wave signals simultaneously in the form of a plurality of visible wavy lines on a recording surface, each wavy line being a series of dots which is the record of a different pair of said electrodes; a digital signal conditioning means connected between said amplifiers and said multi-line channel dispay and recorder to reduce the adverse effects of said muscle artifact signals, said digital signal conditioning means including: A/D means to convert the analog signals from each of said amplifiers into digital signals representing samples of the patient's brain waves; digital data storage means for the containing of brain wave norms; digital comparison means to compare said brain waves with brain wave norms in said data storage means; said comparison means including means to compare the samples of the patient's brain waves with a norm for the amplitude of the sample stored in said storage means, means to detect said samples representing brain waves at a selected level above said norm, means to detect said samples representing brain waves at a selected level below said norm and means to analyze said samples for spikes and sharp waves; connection means to connect said A/D means, digital data storage means and comparison means to provide said signal conditioning; multiplexer means connected to said digital signal conditioning means and said recorder to distribute digital data from said digital signal conditioning means to the various channels of the recorder so that artifact-free brain waves and the said spikes and sharp waves are recorded by said recorder.