Ohm: Represents the electric resistance which will be encountered by an electric current flowing through a column of mercury at 32 degrees fahrenheit; in other words at freezing point, 106 cm. long and 1 square millimeter in a cross section. The unit of resistance is there-fore an "ohm." If a wire was too small for-volt pressure and ampere current of resistance of the wire would be overcome and become heated; perhaps get red hot and melt if above power was very great. The finer the wire the greater number of ohms resistance it has to the foot. If more wires are used resistance is not so great on each. Resistance varies in different metals. The greater the length of the circuit the greater the resistance.
Ampere: Represents the volume of a current which is produced by a pressure of one volt flowing through some conductor that has a resistance of one ohm. It is the electrical current itself and is the practical unit of measurement of rate of flow.
Voltage: Is pressure, that is push power, the force that impels it. Therefore is the practical unit of pressure.
Circuit: When two electric wires from a battery are connected together through any apparatus or instrument it is called a circuit. If only one wire is used and the other side connected with the earth, we have what is called a ground circuit.
Joule: Is the unit of work. If one volt causes 1 coulomb of electricity to pass through a circuit. The volt coulomb is the unit amount of work done independently of any factor. It is equal to 0.738 pounds.
The resistance offered by different metals in conducting electricity are various. Copper is taken as the unit of comparison or 1.
Coulomb: Is the unit of measurement of electrical quantity. The unit of quantity of electricity by 1 ampere in one second.
Watt: Is the unit rate of doing work when 1 volt causes a current of 1 ampere to flow, that is Watts (activity) is obtained by multiplying volts by amperes.
+ Acid Anode: Entrance of current into body.
— Cathode: Outlet of current into the body.
+ Generally stands for "Positive" Pole.
— Generally stands for "Negative" Pole.
E. M. F.: Stands for Electro motive force.
Electrolysis: When an electric current passes through any chemical substances that are in solution there is splitting up of the substances into their elements. Thus the salt is split up, acid being collected at positive pole, alkali at the negative pole. The freed elements at the positive pole are called "anions," those of the negative "kations." Strictly speaking electrolysis is galvano-chemical decomposition.
Water, pure, is a non-conductor , but the saline impurities make it a conductor. Oxygen (anion) appears at the positive pole and hydrogen (kation) at the negative pole.
To tell a positive from negative pole. Electrolysis. Bubbling of hydrogen from negative pole.
Galvanometer between poles' needle will diverge towards the positive pole.
The human body has 20 times less resistance than water. Skin and the sciatic nerve have the greatest resistance. Bone 20 times greater resistance power than muscles. Skin comes next in line, having more resistance power than any other part of the body except bones and sciatic nerve.
Galvanic current employed has generally from 1 to 500 volts interrupted or contains amperage 1 to 300 volts.
Faradic current pressure 100 to 300 volts according to core or coil with current volume of 1-10 to 1-1000 milliampere.
Static machines may have as high as 60,000 volts pressure current volume 1-1000000 milliampere.
Effects on skin, if wanted, use dry with metal brush.
Seventy-five per cent of the body is supposed to be saline water, which is a good conductor of electricity; therefore the more water in tissues the less resistance and vice versa.
Salt water increases conductivity.
Soapy water increases conductivity, doubles current.
Some Differential Points in Galvanism and Faradism.
|Galvanic: Greater amperage. Will produce muscular contraction when Faradic fails. If used, on the head, spine, etc., should only be used for a brief time.||Faradic: Less amperage. Less likely to produce harmful effects. May be applied to head, spine, etc., for some time.|
|+ Positive:||— Negative:|
|Is acid.||Is alkaline.|
|Promotes a clot.||Alkaline dissolves and absorbs a clot.|
|Repels soluble salts.||Attracts soluble salts.|
|Has a drying influence.||Moistening.|
|Diffuses and attracts elements.||Reverse.|
|Lessens nerve irritability.||Increases nerve irritability.|
|Is contracting.||Is dilating.|
|Denutritive.||Increases local nutrition.|
|Lessens inflammation.||Increases local vascularity.|
|Hardens.||Softens and absorbs.|
|Lessens menstruation.||Increases menstruation.|
|Allays excitability.||Increase excitability.|
|In acute conditions.||In chronic conditions.|
|Destroys and eliminates non-vascular tissue.|
|In leucorrhea with profuse secretion.||Dilates uterine canal.|
- Electricity is contra-indicated in fibrocystic or very soft myomas and fibroids complicated with purulent lesion in the pelvis.
- Electricity is also contra-indicated in active inflammation.
- Electricity is contra-indicated in any condition of anesthesia caused by embolism or hemorrhage.
To find place where nerve enters muscle place arm on positive pole and on upper surface, move or trace with negative pole, increasing current, starting with a light current until muscle contracts in some place. This is the motor point. Place positive under foot and trace with negative as above, on leg to find motor points.
Intra-uterine use of electricity is contra-indicated in all irritable conditions of the uterus.
A painful, tender uterus, if it bears a strong current, the pain being relieved while current is used shows that there is passive congestion. If the pain persists or is perhaps increased it shows that there is inflammation.
The electrical current in our body may be in excess or perverted. If in excess there is generally more of a condition of excitation, we find no wrong in the nerve centers, skin is constricted and dry which seems to be different from dryness of other causes. Hard brain work, confinement in very dry rooms, bad conductors of heat, as underwear are some of the main causes. Moist atmosphere, good ventilation and underwear that is a good conductor of heat usually corrects the trouble. On the other hand want of electricity is marked by want of tone, energy, easy exhaustion, relaxed skin, in fact a general condition of relaxation not the result of local or general condition. Moist and poorly ventilated rooms, excess of moisture where working, excessive perspiration, overindulgence in sexual intercourse, excessive urination, excessive moisture in air where working and wearing conductors of heat for underwear. This can be corrected by changing the surrounding environments. Give sunshine, dry air, higher altitude if possible, woolen underwear, good food and in many cases restorative and nerve stimulants.
Positive pole is cool.
Negative pole is hot.
Positive pole of the faradic battery is sedative and the negative is stimulating.
Galvanic negative pole should be applied to fibrous tissue, exudates, tumors, etc., the removal of which is desired. The positive pole of galvanic battery is and can be used in neuralgia or where stimulation is required.
Galvanic current from 1 to 6 or 8 milliamperes stimulates nutrition and causes normal increase of growth, while a current from 15 to 20 destroys tissue and causes atrophy.
Connecting: As to connecting series of cells it depends upon the work we have to do and what force in either direction we look for. Galvanic therapeutic batteries are connected together, unlike elements are joined together in series, that is, the positive the zinc is connected with the carbon, or in other words unlike elements with each other starting with the positive zinc connecting with the negative, the carbon with conducting cords. This in a series gives high voltage, that is, pressure, and is required in passing through bodies of large resistance each additional cell increases the voltage current or pressure. If we require more amperage, that is, more electric current than pressure (the resistance to overcome being small), as for instance the heating of platinum electrode's for actual cautery, in such cases the arrangement must be different. In this case like elements are connected which is termed multiple or parallel. In this case if a number of cells are connected in a series the whole series no matter how many, only give the quantity of amperage of one cell. Galvanic cells that are generally sold only have about a current of 2 amperes. As cautery knives, etc., require from 6 to 18 amperes, it would not be possible to. heat even the smallest cautery knife even if there were 50 to 100 cells joined together. This goes to show that one or two batteries would be enough provided they contain large elements, in order that large quantity of current may be given off, so as to get enough pressure. Ordinary forms of Le Clanche batteries are not practicable, as in a short circuit they polarize very rapidly in a closed circuit. The above refers to galvanic. Caustic galvanic cautery requires a different arrangement.
The Materia Medica and Clinical Therapeutics, 1905, was written by Fred J. Petersen, M.D.