in the treatment of enlargements of the uterus due to subinvolution, but is of little or no value when the enlargement is due to fibrous tissue. It is of especial value in post-partum hæmorrhage, and, from its power to excite the sensibility and contractility of the bladder and rectum, it may be used with good effect when these organs are anæsthetic, or suffer from diminished or lost contractility.

5. From a combination of the first, second, and third induction we obtain the maximum power to excite both sensibility and contractility on the external surface of the body, each additional coil simply giving a decreasing power over sensation and contraction. Applied internally, however, it acts far less powerfully than either of the two previously-named currents; but in the ordinary forms of paralysis of voluntary muscles it will more readily call forth contractions than the current from any other combination of coils.

6. From the first, second, third, and fourth induction coils combined a current is obtained differing from and superior to all the others in its sedative and general tonic effect upon the system at large. It neither acts upon the sensibility nor muscular contractility when applied externally, as does the third current of the series; nor with a tenth or even a twentieth part of the acuteness, when applied internally, that characterizes the second current of the series. For the purpose of general faradization, however, it is the only proper current to use, and for applications to the vagina and uterus, for the relief of many forms of pain, it possesses properties that are invaluable.

Rapid and Slow Interruptions.-All faradic batteries are now provided with some form of the magneto-electric, automatic interrupter; although the rheotome, or current-breaker, may also be governed by clock-work, by the hand, or any other convenient method. Ordinarily, the interrupter, or rheotome, is attached to a spring, as already described, and the interruptions occur with such rapidity as to make a buzzing sound or even a musical note. An improvement upon this is found in some first-class instruments, which enables the operator to increase the interval at will between the shocks, according to the case. In some patients the muscles are thrown into tetanic spasm by very rapid interruptions, and here the slow interrupter is of great service.

Size of Instruments.-Faradic batteries are made of different sizes and various shapes. For treatment of cases of poisoning, or in obstetrical practice, and, in fact, in many medical cases, the small case, such as the Gaiffé, or one of its modifications and imitations, may be all that is required. But for diagnosis and general clinical use, a better one, provided with slow interrupter and a large secondary coil, is indispensable, such as is provided by Otto Flemming, the Galvano-Faradic, the McIntosh Company, and others.

Combined Currents-Galvano-faradization.-No real advantage is obtained by combining the primary and secondary currents in the faradic apparatus; but de Watteville and others have combined the galvanic and faradic currents in order to give greater volume to the latter, and enable it to penetrate more deeply into the tissues.

The Static, or Franklinic, Apparatus.-This is the oldest form of electricity known. It is exhibited when a piece of glass is rubbed with resin, or when vulcanite is rubbed with silk. Now, if either the glass or the resin be brought in the vicinity of some small pieces of paper, or other light objects, phenomena of attraction and repulsion will be manifested. This

condition is known as electrification; and it has been found, from various experiments, that:

1. Articles attracted by the glass are repelled by the resin, and those repelled by glass are attracted by the resin; hence the theory that there are two kinds of components of electricity, called, for convenience, a positive and a negative.

2. Many other bodies, when rubbed together, produce similar phenomena, and become either electropositive or electronegative.

3. Articles which give electropositive electricity when rubbed with one excitant may give the electronegative electricity when rubbed with something else; so that the form of electrical disturbance depends upon the relations of the bodies which produce it. For instance, glass, when rubbed with resin, produces electropositive phenomena; when rubbed with fur it is electronegative.

4. The electrical conditions of both articles are disturbed, and to an equal extent, the quantity of electricity upon the glass rod being exactly equaled by that on the resin or fur.

5. The amount of electrical difference between the two bodies is known as "the difference of potential," since it is the measure of the force which would have to be exerted in order to restore them to their original state of equilibrium.

6. Electrical phenomena are produced in bodies brought into the vicinity of either a positively or negatively excited electrode. This is induction, and the electricity thus caused is known as induced electricity. It is found that, under such circumstances, in a body capable of conducting electricity, the form of electricity will be contrary to that of the electrode, and they will be mutually attracted. Hence the rule: "Unlike electricities attract, like electricities repel, each other."

7. Electricity of this character is confined to the surface of bodies, and can be confined or stored up in appropriate apparatus,-i.e., in what is known as the Leyden jar, and is, therefore, known as "static electricity."

8. A body is charged by conduction when its electricity is conveyed to it through a rheophore or metallic connection. It is said to be charged by induction when the electricity is due to the action of surrounding bodies. without contact, as already explained.

9. The phenomena of static electricity resemble and are identical with electricity from other sources, when of small quantity and exceedingly high tension (or electromotive force). The terms positive and negative, therefore, resolve themselves into differences of potential, the current flowing from the higher to the lower potential, as in the current from the galvanic cell.

The foregoing brief résumé of the phenomena of static electricity is a necessary introduction to the study of electrostatic machines. They consist, essentially, of an apparatus designed to convert motion into electricity by means of friction and induction.

Forms of Static Instruments.-Electrostatic machines are either frictional or induction machines, the latter requiring to be independently charged before they will act. Frictional machines are identical in principle with the experiment first mentioned, where glass was excited by rubbing. In its usual form the glass is a circular plate or disk suspended from its centre, and capable of revolving when turned by a crank. It is provided with a rubber or cushion of leather covered with amalgam of tin and mercury, this be

By connecting the transformer with a static machine the current undergoes a complete change, rendering its application painless even when applied to the most sensitive organs. As the current is of higher voltage than that of the static induced, the spark from one pole only is, as a rule, used, employing either a metal or carbon point, or else the glass tube lined with tin-foil (see diagrams at top of page). The effect of the hyperstatie spark on eczema and acne and in some cases of local pruritus has been extremely gratifying. In various forms of neuralgias, where irritation is wanted, any resisting medium interposed between the high-tension spark and the skin (such as covering the lesion with oil) will produce increased pain and irritation. One is able, therefore, by regulating the spark-gap between the jars, and using oil or not, as may be required, to obtain either an absolutely painless and almost fugitive effect, or, on the contrary, produce a very marked cutaneous reaction.

ing slightly pressed against the side of the plate, so as to cause friction when the plate is revolved. There is also a comb of metal, the points of which do not quite touch the surface of the plate. The cushion and comb are connected by means of metallic conductors, each with one of a pair of brass balls, which are the poles or electrodes of the apparatus. When the glass disk is revolved the rubber excites positive electricity upon the glass surface, and is itself negatively excited; owing to the amalgam, its charge is carried to the electrode in connection with it. The surface of the glass which is positively excited passes under the comb, which conducts the charge of positive electricity to the brass ball corresponding with it. The charge of positive electricity steadily increases, until the difference of potential is so

Diagram of the Piffard Hyperstatic Transformer.

J, J, Poles of static machine. F. Muffler for concealing spark and suppressing sound. F. F, Spark controllers. H, H, Connectors with static. D, D, Removable ends of E. Al, Screw-hole. A, Screw-hole. A, Screw for All and Al. B, B, Arms for connecting C and C. K, K. Screws for tightening C and C. L, L, L, Screws for holding jars. M, M. For cords and electrodes. Directions: Connect the poles of your static machine with the muffler at II, II, this by the tubes with the projecting arm of the jars (C, C), and regulate the strength of the discharge by the spark-controllers.

great as to cause a disruptive discharge between the two poles. This temporarily restores the equilibrium of the glass, which passes again under the rubber and the phenomenon is repeated. The pole in connection with the comb which is positively excited will, if brought near the negatively-excited pole, discharge itself as a spark passing between the poles, when the difference of potential is sufficient to enable it to jump across the intervening space. If it is desired to apply this form of electricity to medical purposes, light brass chains or other conductors are attached to the poles, and by means of suitable electrodes sparks may be drawn from different parts of the human body. If we insulate the patient by seating him upon a chair having glass castors or a stool supported by glass, we may connect him with either pole,