anterior spinal cornua, from disease of these cornuas, or of the nerves proceeding from them. It is not inconsistent with the preservation of motility; is present in anterior poliomyelitis, lead paralysis and severe cases of paralysis from peripheral nerve lesions.

FIG. 6.

This diagram represents the points of entrance and exit of the current in a nerve submitted to percutaneous excitation with one electrode, and the consequent formation in it of two zones of opposite electrical character; anodic and kathodic. The anode is supposed to lie over the ulnar nerve, whilst the kathode rests on the trunk. The polar anodic zone is shaded. The two

brackets show that, owing to the diffusion of current, the unipolar excitation of the imbedded nerve sets up in it a descending as well as an ascending current. The signs indicate that under such circumstances the electrotonic condition of the nerve in the neighborhood of the electrode may be found the opposite of that set up immediately under the electrode.

In partial De R the galvano-muscular reactions are the same as in the complete form, but the faradomuscular and the galvano-nervous and farado-nervous reactions are normal or slightly diminished; here the trophic influence is in some unknown manner cut off from the muscles, but not from the nerves. It occurs in amyotrophic lateral sclerosis (not always), progressive muscular atrophy (of central origin), bulbar paralysis, mild acute poliomyelitis, and in mild forms of peripheral paralysis.

IV. Changes in sensation.-Electro-diagnosis only enables us to ascertain the presence, location, and degree of hyperesthesia and anæsthesia.

V. Special senses.—We have as yet no certain data in the diagnosis of the diseases of the organs of vision.

Of taste, we can only judge whether it be present or absent.

The presence of galvanic hyperexcitability of the acoustic sense affords an indication for treatment in certain cases where the hyperexcitability is accompanied by subjective noises; upon KC these noises often disappear at once and completely.

PRACTICE OF ELECTRO-DIAGNOSIS. The patient is so placed that symmetrical parts are in the same position and equally relaxed. A large, well-moistened electrode is fixed over the sternum, and a smaller one with interrupting handle used as the exciting electrode. Comparison of symmetrical parts is best, but if the disease be bilateral, some other part, the condition of whose reactions is known, must be selected. First, with a current of ten cells, having a galvanometer in circuit, ascertain the amount of deflection when the electrode is placed over each point to be tested; by this means we may eliminate the error arising from difference in tissue resistance. Mark the points tested so that the electrode may be placed exactly over them, and see that the duration of closure and opening is exactly the same on the two sides. Now, with a slowly interrupted faradic current, note the amount of withdrawal

of the cylinder at which the first contraction occurs, and also the maximal contraction with very strong

currents.

Next, with the galvanic current, ascertain the minimum number of cells with which a contraction occurs upon KC, AC, AO and KO, in the order given ; also note the manner of the contraction.

A bifurcated rheophore may be usefully employed in these experiments, enabling us to compare reactions on different sides of the body at the same time and with the same current.

In testing sensation, the skin should be dry and dusted with some drying powder; the wire brush or Erb's electrode may be employed.

In examination of the eye, the active electrode is placed over that organ; of the ear, in front of the tragus or introduced into the ear, which has previously been filled with water. The sense of taste is tested by placing a small kathode over tongue, etc. Various electrical explorers have been invented for the purpose of detecting the presence of metallic foreign bodies in the body, but so far they have not been satisfactory.

CHAPTER V.

ELECTRO-THERAPEUTICS.

I. Magnetism.-There is much difference of opinion both as to the curative power of magnetism and as to the manner in which it should be applied. The most remarkable cures have been obtained in those cases where the symptoms were subjective, and the influence of psychical impressions could not be eliminated,-viz., in the various manifestations of hysteria, in neuralgia, anesthesia, and chorea. In neuralgia the south pole is stroked over the seat of pain or held upon it; in the other affections named, a variable number of horseshoe magnets are bound upon the parts for a variable length of time.

Both permanent and electro-magnets are also successfully used for the extraction of bits of metal from the interior of the eye, a magnetized needle being passed into the neighborhood of the foreign body.

II. Static Electricity.-The static induced current may be advantageously substituted for the faradic