time to time, of the original model, which have not been here specified by me; but as they do not in any way affect the principle of electrical induction, they are not of importance in this connection.

In the original Holtz machine a charge was primarily effected by rubbing a piece of ebonite briskly with cat-skin until it became highly charged with negative electricity, and then applying it closely to one of the paper collectors on the stationary plate of the machine. By the "law of induction" the comb opposed to this paper collector becomes electrically excited immediately. It at once deposits positive electricity on the side

FIGURE 10.-Holtz's static induction machine, with horizontal plates.

The plates have neither windows nor armatures, and they revolve in opposite directions.

of the revolving plate nearest to the comb, and takes negative electricity away from the revolving plate. Thus the revolving plate becomes positively electrified to a very high degree at this point.

Now when the wheel is made to revolve to that point where it meets the other paper collector upon the stationary plate, induction again takes place. Negative electricity is deposited, (1) by the collector on the opposite side of the revolving plate (the side nearest to the paper collector) and (2) by the metal

comb; at the same time positive electricity is taken from the adjacent side of the revolving plate by the collector, and also by the metal comb, from the opposite side of the revolving plate. This interchange of electricities charges the "positive pole" of the machine.

The revolving plate (now excessively charged with negative electricity) goes on to the next paper collector. Here a similar exchange of electrical conditions occurs. The negative electricity is taken from the revolving plate by both the paper collector and the metal comb, and positive electricity is given to the plate in exchange from both of these sources. Hence the

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'negative pole" becomes highly charged.

As long as the revolving wheels are kept in revolution, this interchange of electricities continues at each of the poles; hence the accumulation at each pole soon becomes sufficiently great to allow of an escape from pole to pole in the form of a spark, or into the atmosphere as a "luminous brush" easily seen in the dark.

STATIC ELECTRICITY AS COMPARED WITH GALVANISM.

It has been computed that the electro-motive force of a Holtz induction machine is 52,000 times as great as that of a Daniell cell (or 52,000 volts). It is not affected by the velocity of rotation.

The quantity generated is proportionate to the velocity of rotation and the number of wheels employed.* It is modified also by the moisture present in the atmosphere.

The internal resistance of the machine diminishes rapidly with increased velocity of rotation. It is not influenced by atmospheric conditions.

STATIC ELECTRICITY IN MEDICINE.

The revival of static electricity (or Franklinism) as a therapeutical agent from the oblivion into which, for nearly half a century, it had unaccountably sunk, has been occasioned by several factors. Among these factors the following may be prominently mentioned:

(1) The awakening of the profession at large to the fact that electrical currents of different kinds have distinct therapeutical actions.

These are not to be attributed to or confounded with the strength of the current employed, or its method of application. The effects of faradization, galvanization, and franklinization

* On this account I have lately increased the size of the drivingwheel, so as to ensure rapid revolution of the plates of the machine.

upon animal structures differ widely in many respects. The time has come when an intelligent physician cannot justly condemn all forms of electrical treatment of any individual case, because he has failed to obtain satisfactory results with one of the above-mentioned currents alone; even if he has employed that particular form of current with the highest possible skill and judgment.

This is an error into which many are unwittingly led. I could report (if time would permit me to do so) the details of several cases where a failure to employ the proper current has proved most disastrous to patients. One instance of this character (which was happily aborted) impressed me so forcibly at the time, that it is possibly worth narrating:

A patient, who had accidentally severed the musculo-spiral nerve by a pistol bullet, was sent to me some years since for diagnosis, and to confirm or reject an opinion which had been expressed by a physician of prominence, namely, that the only hope of cure lay in a surgical operation for the uniting of the severed ends of the nerve by sutures. This opinion, as I found, was based upon the fact that the faradaic cnrrent had failed to produce any movement in the paralyzed muscles; and that several months had already elapsed since the accident-during which time the hand was steadily becoming more and more deformed by contracture of the flexor muscles of the hand and forearm.

My examination of the patient showed, however, that a galvanic current produced violent contractions of the paralyzed muscles when passed through the injured nerve (one pole being placed upon the sternum as a neutral point, and the other upon the musculo-spiral nerve); and the galvanic reactions of the nerve and its muscles furthermore indicated marked "degeneration" as having developed in the nerve below the point where it had been divided. Thus, the question of the advisability of an operation was decided positively in the negative. The nerve had already united.

In about eight months the injured nerve was completely restored by the use of the "static spark"; the contracture had disappeared; and to-day the patient can see no difference in the usefulness of his hands.

(2) The improvements which have been made in machines for the generation of static currents for medical purposes have had much to do with the revival of this method of treatment.

Some of the cases reported in the earlier encyclopædias, and

antiquated works on electricity, are fully as startling as those now encountered, when treated with the improved machines; but, on the other hand, many failures to obtain good results must of necessity have occurred in olden times from the imperfect apparatus depicted in the scientific works referred to. Later, I will discuss the various improvements which have been made from time to time since Holtz first devised the present model of an induction machine (1865).

(3) Improved methods of administration of static currents have added materially to the effectiveness of this agent as a cure of disease. Some of these methods were unknown in earlier times (as far as my research goes to show).

(4) It is now known that a considerable quantity, as well as length of spark, is essential to the successful use of a static machine in medicine. Many of the static machines sold to-day are practically worthless, save as a toy; because they do not produce a sufficient quantity of electricity. The requisites of a static machine for medical purposes will be touched upon later.

(5) Experimentation with this agent seems to have confirmed the views of its enthusiastic advocates of the present day, and to support the accuracy of many of the observations reported in old scientific works. The incredulity of the past is rapidly being overthrown in respect to this method of treatment; and the special fields in which it proves of the greatest service are being definitely mapped out by those who are scientifically recording the results of its administration.

For the past few years I have devoted considerable attention to the improvement of the Holtz induction machine. Some of the results of my experimentation have already been published. The machine now described to you is in some respects an improvement upon the one which I originally introduced to the profession through the Medical Record of October 17, 1885. I have modified the charger originally used by me, so that it now bears upon the outer revolving plates above the metal combs, instead of passing between the central revolving plates. I have found that the application of cat-skin at this point on the outer plates awakens the machine into action (when not charged) with greater rapidity and certainty than at any other part of the machine. Furthermore, there is no longer any difficulty in making the contact between the charger and the glass when the wheels are revolving rapidly;* while, with the old charger, the

* A slight touch of the charger of short duration upon revolving wheels, repeated at intervals of a second or two, is more effective than a long continued application to the wheels of an induction machine.

springing of the rubbers often rendered their insertion between the revolving plates (which are in extremely close approximation) a matter of some little annoyance at times. This modifi

FIGURE 11.-Holtz induction machine, as improved by the Author.

cation in the charger has entailed a slight change in the mechanism by which the rubbers are brought into play when needed.*

Again, although chloride of calcium is not required during the cool months in this particular machine for the purpose of *In some models of the present day, the charger cannot be raised from between the revolving plates. This is a serious defect.

NOTE.-The following description of this machine is quoted from the author's article in the Medical Record, October 17, 1885:

"I would call the attention of the profession to an improved static machine which has been lately devised by me.

"It is the result of many months of experimentation, and is the outgrowth of the dissatisfaction which all other devices for generating electricity by friction have afforded myself, as well as others who have employed them. By those who have had experience with static ma