_α_. The Faradic Reactions diminish rapidly in degree in both nerve and muscles from the third or fourth day, and in the nerve they are, as a rule, completely lost at the end of from ten to fifteen days. In the muscles complete loss of faradic reaction is noted only somewhat later, and is absolute. A return of musculo-faradic contractility is a most positive sign of recovery of the nerve. _β_. The Galvanic Reactions.—In the nerve, distal of the lesion, the result is similar to that stated above—viz. after a few days (from five to fifteen) all reaction disappears. The anatomical cause of the complete {67} loss of the faradic and galvanic reactions in the nerve is its disintegration by the Wallerian degeneration. In the attached muscles the phenomena are widely different, and present interesting and complicated variations. In the first place, during a variable number of days there is increased excitability—_i.e._ the paralyzed muscles, deprived of innervation, contract to a much weaker current then do the homologous normal muscles. This is best shown in cases of peripheral facial paralysis (Bell's palsy) in the second and third weeks, by placing the electrodes in the median line, one upon the cervical vertebræ, the other (a small testing interrupting electrode) on the chin; on closing a very weak current of from four to eight elements it will be seen that the muscles on the paralyzed side of the face (the lower muscles) contract distinctly, while those on the normal side remain quiet. In the course of time, many weeks usually, the excitability diminishes, and falls below the normal, and in some cases ultimately disappears. These are known as the quantitative changes in musculo-galvanic reactions. During the long period preceding recovery, or without it, various qualitative changes are also observed in the reaction. The normal general formula of CaCC > AnCC (with rapid, jerking and full contractions of the muscle) becomes CaCC = AnCC or CaCC < AnCC. Often, too, distinct opening contractions occur, usually AnOC. The muscular contractions also tend to the tonic type or tetanus, expressed as CaDT or AnDT, etc. The form of the contractions obtained is much altered. Throughout a practically endless period in some cases, or until regeneration of the nerve takes place in others, it is observed that musculo-galvanic contractions are delayed, are slower, less jerking, or assume an undulating wave-like character, easily passing into tetanus. This change from the rapid, jerky, and full normal muscular contraction to one which is slow and wave-like we consider to be the most positive and reliable evidence of neuro-muscular degeneration and of the cutting off of the spinal-cord influence. Fig. 4 shows the characters of a human degenerative myogram contrasted with a normal one, Fig. 3. [Illustration: FIG. 3. Contraction of Normal Abductor Indicis, CaCC, with strong current (Amidon[2]).]