In 1906 the Dutch physiologist Willem Eithoven, invented a method to register the feeble voltages that occur among differents areas of the human body, by means of a string galvanometer. For his researches he was granted with the medicine Nobel award in 1924. To improve the testing accuracy, later on the string galvanometer was replaced by a more sensitive apparatus, the loop galvanometer, in such away the voltages of the cardiac muscle generated in the skin surface could be measured and recorded in graphics as kown as cardiogram allowing to observe the heart functioning status. Certainly such new discoveries gave birth to the electrocardiography.

Fig. 352 ilustração do novo campo da ciência médica, a eletro medicina.

Thus the electrocardigraph became an invaluable tool to undertand of heart diseases since by a carefull studying of the recorded cardiogram for a few hours at an early stage, it was possible now that a heart attack could be prevented by mean of a more accurated technique the vector cardiogram.
It consists in the use of an oscilloscope, which offers the possibility to show in a panoramic overview the several voltages generated by the heart muscle, thus allowing the physician to be able in evaluating their interrelationships.
Soon the technique developed by Einthoven was used for the measurement of even lower voltages, about 30 microvolts, which were generated by the brain detected in several areas of the surface of the skull. In this way through the encephalograms the physician could be able to study the behavior the the brain, which was a step forward in the science of neurology.In spite of the aforementioned techniques around 1950 several other types of electronics aids for medical diagnosis were availabe for a detailed study of the human body. Thus sensitive photocells used in advanced types of colorimeters allow accurated biochemical analysis for many components fgound in the blood stream such as uric acid, hemoglobin and creatine, fig 352.
The classical medical diagnosis methods by auscultation and percussion were replaced by advanced and precise cliynic techniques. Among them are: diathermy, myography and ultrasonic procedures as well as including an array of patiente computer controlled monitoring electronic devices. Table 4.

TABLE 4 – SEVERAL TYPES OF CURRENTS USED FOR ELECTROTHERAPEUTICS PURPOSE IN THE LATER FORTIES.
CURRENT TYPE	WAVEFORM	OBS.
GALVANIC		Galvanic current is simply D.C. up to 75 V at 1 to 20 mA.. It is obteined from batteries, D.C power lines, or most commonly from A.C. lines using selenium or vlave rectifiers. It is used for treatment of certain types of painflu inflammations and iontoforesis.
PULSANTING GALVANIC		Similar to the aforementioned, whose pulses are are produced by electromechanical devices, for instances such types of relays. It has the same electrotherapeutics as the Galvanic current.
SURGING GALVÂNIC		It is a a D.C. current whose amplitude is varied periodically by motor-driven variable resistors, Thyratron valves.
FARADIC		This modality is similar to the pulsating Galvanic, except for a slight negative dip, a sharp positive peak, and higher frequency 1 to 2000 Hz. Its amplitude is about 75 Volt at maximum 1 mA. It is produced by Faradic generators or coils, sometimes called inductoriums. It is used to stimulate injured muscles as well as muscles whose nerves are receovering from diseases or injury.
SLOW SINUSOIDAL		It is a low-frequency Galvanic current – 5 to 30 Hz produced by electro-mechanical generators or generators operating with Thyratron valves. It is used to stimulate injured muscles.
SURGING ALTERNATING		It has the same voltaga and current as in the Galvanic type whose 60 Hz frequency is surged by a thermally aactuated interrupter or a motor-driven generator. Such type of current is used in the electric shock terapy.
STATIC WAVE		Static waves are generated by high-voltage rotating friction machines, but a very small current around 1 mA. Due to its complexity has few practical applicatin in electrotherapeutics.